Long post since I don’t think you can upload .doc files. The post is a summary of my look at using the iPad for building 3D models. It’s mostly about tools available, requested under another post. This isn’t an exhaustive review of iPad 3D printer oriented apps, it is what I have learned so far. Also note, I’m not a pro. My guess is people that use these tools to make a living would likely have a very different view, but then I doubt they are doing much design work on an iPad anyway :-). I don’t have an Android laptop so can’t say how much this would apply to that world.
Bottom Line Up Front: For the most part, none of these tools are going to replace a desktop, but many of them get close, esp. if your not a power designer. A few are actually pretty good and you can do a lot with them, but they are all pretty much first or second generation apps and need some maturing. The two big issues for me is functionality and whether they put a lot of thought into the UI. Some of the tools have nice touch focused UIs, some look like they implemented a desktop paradigm on a touch screen. I learned to program from the engineering department and when I took a course from the CompSci department the prof told me I was just a Fortran programmer using C++ That what some of the UIs look like, classic tool UI implemented on a touchscreen 
– I played with some of these tools on the iPad screen but also with AirPlay to my 55" TV. Love working on that size screen! You have to Mirror the iPad which means it didn’t fill up my TV screen but it was still bigger and easier than connecting to a 27" monitor.
– Output (for printing): I skipped over a number of nice looking apps because of how they output. Some support 3D printing directly with an .stl format, many don’t. In those cases they may have .obj or DWG output which we can use indirectly but some only support 3rd party printing. Sage 3D Printing is a good example of this as is Blockify. Blockify looks like a great tool for kids to use (basically like building with lego’s) but the only way to print is to send it wirelessly to a printer or have them print. Sage is a good example of letting geeks run the world. Looks like a nice tool but besides the fact we can’t print with it, it’s biggest flaw is lack of information. The information they provide on App Store and their website is just awful. Maybe that’s the goal…make the price cheap enough people will buy it cold but a marketing guy would just roll his eyes. Sigh. One or two have .stl output but only via wireless. As far as I know there isn’t a way to send files to the Form1 wirelessly. If someone knows how to please let me know!
– I should have noted, but didn’t, which have desktop versions that make it easy to shift back and forth. What I did notice that when both exist the desktop version is usually more robust. Go figure.
– None of these apps are overburdened with documentation. Programmers like to program, don’t care about users. Our world is controlled by Sheldon’s 
That said most have YouTube (usually, other video sites sometimes) demos and/or tutorials. I’m beginning to think YouTube is the new documentation format, which for these kind of tools is actually pretty OK, unless you just need a quick reminder.
– I skipped over a number of apps that looked like they were focused on things like making little toys and/or for kids (I don’t have kids around so I didn’t explore them, but they do look like they could be fun - esp. since they can get a physical rendering of their design). A few examples here are:
Modio: Looks like a fun little app for building characters. Claims all models print without supports (umm…). If it works as advertised, could be a way to get kids to quit handing you drawings to make models of - put them on the iPad and have them create their own print ready models
Draw in 3D: Another tool that looks like it could be fun for kids. Think finger painting in 3D
There are others but you get the idea
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3D CAD Like Apps:
123D Design: Probably the winner. Functionality very similar to the desktop version but optimized for a touch screen. Biggest issue is lack of 2D tools. You can get them but must go Premium, which is far too expensive for a casual user. Price: free. Good YouTube videos show you how to use it but most things you can figure out on your own. A few nice features for amateurs such as the various features to connect 3D objects without paying the ‘what plane am I in’ game.
CADBox: As I remember it was $4.99. Not bad, pretty classical approach to CAD. No 2D but also lacks tools to manipulate faces or edges. Scale works in %, a technique that is IMO useless. All that said, you can with a little practice do everything 123D Design can do.
Polygonify: I liked the way the designer approached the UI but the tool isn’t quite ready for prime-time. The few examples they show are quite impressive but I have yet to be able to really figure out the basics and the lack of documentation doesn’t help. I did send the designer a note and he pointed me to a couple YouTube videos (haven’t looked at them yet). He did say he was working on documentation. Will be interesting to watch this one mature. Don’t remember the price, only a few bucks.
AutoQ3D: Interesting, I had to search on 3D modeling in Safari for this one. It’s $30, looks pretty nice but at that price I didn’t try it. Worth looking at though. I will buy it, will let you know later. Does output in .obj and .stl I always look for .stl output but .obj is a useful format. There is a version for just about every platform. The iPad version looks like a lite version of the OS X version. Also looks more robust than 123D Design. UI in videos looks like some thought was put into a touch interface but I expect Design is still a good tool for the novice.
3D Model Builder: Somewhat strange UI. Looks like something that would have been built 15 years ago! That said, they advertise ease of use and I would say they made that objective - for what I could do. It locked up twice on me so I wasn’t able to really dig into it, guess there is a note heading to the developer. Cost: $2.99.
BTW, these guys have a lot of separate viewers (.stl, blender…) that some may be interested in
FingerCAD HD & Finger3D HD: $10 each. I haven’t used these yet. CAD looks to be a classic tool with UI improvements for a touch screen. Focus seems to be layout in 2D then extrude. 3D is a modeling tool, work in 3D, not the 2D looking focus of CAD. The tools are useable as a set. Out put in .obj, DXF and a few others, but no .stl. On the surface it looks pretty robust and there is a MAC version. I may give it a try
Classic CAD:
There are a bunch of 2D focused CAD tools which I didn’t dig into much since there are better choices for the 3D printer world. However some may prefer these tools for a variety of reasons to start a design. Included one as an example.
AutoCAD 360: From the AutoDesk folks. Two versions, the free one allows viewing of DWG files and some editing but it is really designed to be used with the Desktop (or Pro version but that wouldn’t make sense). The Pro version is a lite version of the Desktop version. Pretty complete tool set but requires an annual subscription, which is either $50 or $100 (difference seems to be on-line storage capacity). There’s also a $5/month option which would work if your only using is once in a while I suppose. Probably a good choice if you know AutoCAD or plan to move in that direction. Haven’t used it, so not sure how good the UI or how steep the learning curve is. As of Dec 2014 they are showing both to be in beta. Does support a few file formats, like DWF/DWG, didn’t see either .obj or .stl Guess that means a converter would be in your future if you go this route for 3D printing
vueCAD Pro: $999, nuf said
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Artist Apps (not the best term, wanted to separate the 123D Design type from the 123D Sculpt type)
There are two subcategories here. Simple, focused, fun tools like Draw in 3D are fun but of little practical value if your trying to design something like a fancy vase or Katnniss. I did download it and have let a young niece create something then I printed it.
123D Sculpt: Haven’t used yet, like the desktop version, it’s free, tries to mimic modeling in clay, can 3D print your weird creations.
Artist3D: Nice little app, sort of a cross between a tool like 123D Design and 123D Sculpt. Probably need to watch the short intro video to get the idea but with that and a little practice to get comfortable with the interface should be modeling pretty quickly. UI gives you control at the polygon level, where tools like iDough are more like working with clay
Forger: Similar to Sculpt. Tried to use it once, rough start, Can output .obj which you should be able to bring into 123D, then output in .stl
iDough: Focus is to mimic modeling in clay. You start with a round blob and work it into whatever shape you shooting for. UI looks straightforward, the learning curve will be more about shaping clay than how to use the tool. YouTube video demos an example. Outputs in .obj Price $7
Morphi: Did download it but haven’t played with it much. UI seems well suited for iPad. Outputs .stl Once you get something from the App Store you can’t go back and find the price but I think it free. Does have an in-app purchase called Shapes for $4. One nice feature is that you can change the design ‘table’ (aka grid) to be sized IAW your printer - and Form1 is a selection option (V2 released late Dec 2014). I did see on the YouImagine model repository site someone is posting Morphi models. Probably worth more of my time to learn
Verto Studio 3D: $13.99. Haven’t looked at it much but it looks like a pretty robust tool, similar in functionality to tools like Blender. Their App Store write up says it’s useable by pro’s and amateurs alike. This does look like one powerful tool. I’m no expert here but I expect anyone designing for the Form1 would be hard pressed to find a need this tool wouldn’t cover. Found quite a few Youtube tutorials and (surprise!) there is a built in manual. I also expect the learning curve for amateurs isn’t as bad as Blender but expect to spend some time learning it. If you have a background in these types of tools, should pick it up quickly. Bet it would work well with my 55" TV. Works with .obj files
Sketching Tools:
Many of the CAD tools have 2D sketching functions so not much reason to look at separate sketching tools, however I did find one Sketch It, Make It that I liked the potential of. They really have taken a novel approach to the UI that I think embraces the potential of a touch screen. Although useable, it lacks some functionality that would make it a viable tool. If they continue to mature it, I could easily see me doing 2D here then outputting to (say) 123D for extrusion. Right now, it only outputs .stl but it does have a nice feature some may like, it also outputs for laser and CNC machines. Everyone should get it to keep the developers motivated
Viewers and Converters:
There are bunches of these. I haven’t looked into them since I do this kind of thing on my MAC, but down the road… I will mention two for now:
– There isn’t a SketchUp version for the iPad but there is a warehouse viewer. However you have to be careful with SketchUp since it’s REALLY easy to build models you can’t print. There is a Dummies book for using SketchUp for 3D printing that gives you the do’s and don’t. Plus, unless it’s changed you will need a third party converter. I only mention this because there is a warehouse viewer and it is possible the PreForm built in tool can fix some of the issues but I have no personal experience.
– As noted above, the company that makes 3D Model Builder has a bunch of converter and viewer apps. In the App Store, click the link to other apps by this deverloper
– PrintAbles: Thingiverse viewer. A third party tool. Has some nice features for looking at Thingiverse models, one being a dynamic 3D model viewer.
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Closing Comments:
– Buy a few apps, even if just to play with. Personally I don’t mind spending a couple bucks to support developers of tools that have potential - keep them motivated
– Although I was focused on tools to use with my Form1 and Solidoodle. But there are other interesting apps starting to appear that even though you have to send them off for printing, they are a creative use of the iPad in this overall space. UStatue is one example. Send them a face photo and they will print you a statue. Send your kid off to college with a small bust of the parents - so they don’t forget you
And finally, searching in the App Store largely sucks. When I search on 3D print/printing/printer I get slightly different results. Some of these I only found by searching with Bing and there was one artist like app that started with an S I found once but no amount of searching allowed me to find it again. Sigh.