I've initially bought the iPad version and had a blast with it. I just reached Barbarossa and wanted to restart the campaign because I thought I could do better (and besides I only MV'ed Sea Lion 40). Then I installed the demo version of the PC and became torn between choosing one of them to go on.
To be frank, the iPad version is flawed compared to the PC's, with some features may be fixed while some may not at all:
- The iPad's "fullscreen" mode should have one extra button (or a window which allows to be toggled on or off) to allow you to see unit's stats
- Library can only be accessed from the main menu
- Library is lacking critical information which are available on PC (terrain, movements, campaign routes)
- No combat details (ctrl-right click or L on PC), this is a huge issue as so many critical things can't be known without this function (e.g. low altitude attack causes defense penalty!)
- Blurry graphics, this is extra obvious when directly compared to the PC graphics
Now, I'm pretty sure the former 4 points can be fixed with a (hopefully soon) patch, but I'm not sure with the 5th. I guess it's very possible to introduce the original hi res graphics without impeding the performance, but it's of lower priority as lots of more important developments are going on (Soviet Corps, patching PC/iPad versions, Steam release, etc.).
The PC version isn't just superior by having the missing features and crispier graphics, but also by moddability (though I don't play with mods), supporting huge monitors and resolutions (playing the game on my 27 inch screen with 2560*1440 is a MAJESTIC experience), lower eye damage (the iPad IS closer to my eyes than a PC screen), and one major concern: the sustainability.
By sustainability I mean how the developers are willing to commit in the long term on a specific version. Supporting multiple platforms of a single game is a daunting task unless you're EA or something big like that, and can afford different departments to handle the updates and other supports for mobile platforms. I guess Panzer Corps' core players are PC users, at least for now. The PC version will almost always be supported, not to mention it will get the latest patches and newest features. But the iPad version will inevitably see delays on such support, and there is even a possibility that it may cease to update, especially if the iPad version is not as profitable/popular, or there are major changes in the mobile landscape (incompatibility of new iOS versions, decreasing iOS popularity, etc.). I know it's too soon to make such guessworks, as the game has just released for a couple of months on iOS, but I do have experienced many good iOS port games dying due to lack of support (Puzzle Quest 1, Battle for Wesnoth, Sid Meier's Pirates, etc.).
I guess you may half-jokingly to so say "then buy BOTH!". Guess what, I do NOT mind doing so as the game is simply brilliant. But there is one final problem: lack of save synching between iPad and PC version. I know this is technically not possible to create a solution, as I haven't seen a single game that has a useable cross-platform synching feature. It would be such an annoyance if one day the iPad version stopped getting supports (it's simply a consideration of risk), all my savegames are stuck in it, or if I'm playing mainly on the PC and need a Panzer fix while on the road or away from home, yet unable to do so because the saves are not on my iPad.
Finally, being torn between making such a iPad vs PC choice means the iPad version do have features that are so attractive that the PC version can't provide at all. For me, using a touch screen to choose and order units is so...intimate. Using my finger to point at my troops and get their acknowledgements, then point at a city to see them move over there, and pointing my finger at an enemy battalion just to see my troops open fire on them...it really makes me feel like a WWII general making real orders with hand gestures on a real battlefield (after all, WWII generals don't make orders with mouse clicking!). And on the iPad I can zoom into the action and take a more tactical view & thought too. Finally, NOTHING beats the capability to fix my war urge at any time and any place. Besides, the iPad version is cheaper

My verdict? I guess I would continue playing on my iPad for the moment, and I absolutely hope the patch will come out this week or the next (AKA ASAP). And I sincerely hope the iOS version will attract sufficient old or new players, and therefore receive adequate long term support.