We use both the full size and the mini ipad with Foreflight. Not much difference between the two, but I can fit my ipad mini on a kneepad or on the yoke clip on. Can't do that with the full size. Foreflight works great and I have no reason to change now, but I have seen the Garmin product at their mock up booth at NBAA and it's pretty snazzy.
Now, none of this will improve your flying, so if you are training I'd go with as little bells and whistles as possible, and then use them later once you got the basics down. DME,VORs and paper charts are a good way to learn. Get that down and you won't skip a beat if the ipad freezes up on you, like it has on me.