Here's the issue; you probably already have a phone that runs Apple iOS or Android, have some form of laptop that you've used for a while that works for you and possibly a home PC that you can get some processor/space heavy work done. You have to decide if you want yet another device to support while you have the luxury of tons of free time in medical school.
I recommend the iPhone 4s or the Samsung Galaxy 3 as the new phone if you're in the market for a new device is really portable. "Rooting" or Jailbreaking" is possible on both, so you can put whatever you want on either one for a substantial discount if that's driving your decision. If you've done that, you can transfer files back and forth whatever way you want and avoid iTunes completely. Torrents of medical apps, ebooks and movies are illegal but the price is right for some people with the technical skill to get them on any device and that's I'll say about that.
Either of these phones are also reasonably priced now that the next device is soon to be out in the next few months. This is the way it is every year with Apple and Android phones. Any of these will fit in your white coat without a problem. Stay with iOS 5.x for iPhone and at least Jelly Bean releases that they run on for the best functionality and compatability with everything else.
If you don't have a laptop, focus on that first and the novelty of having a tablet that you can use your stylus on wears off when you have to hold the screen with one hand while you're writing with the other. The glare factor when in class is also a problem when you're under the bright lights. Both these issues happen with most tablets with the amount of use you'll get in med school.
If you absolutely have to have an Apple tablet device, get a refurbished iPad 3 and save yourself the money. The spec differences between that and an iPad 4 are not enough of a reason to spend the money on them. I love Samsung devices for their screens and build quality, so I would get one of their tablets above any other. MBP can use normal 500GB drives that make more noise from it or the fan used to cool it while the or Air has a flash drive that is more expensive to use for Apple and they have no problem passing on the extra cost to you. Spending over $1000 for any device and getting around 128MB of drive space is ridiculous.
Just please don't be "That Guy" that sits down in the lunch room of your school and proceeds to take the iPad out to plug it into his laptop USB to sync, then his phone into the laptop to charge and sync and finally plugs the laptop into the wall outlet to make sure he doesn't run out of power. I've seen this a lot recently and it's really easy to see that his priorities may not be in the right place. If you want to do this, you may as well carry this one around; it may be a bit lighter:
You will quickly find out all the problems you'll have doing a physical exam with the chance of hitting the patient with the tablet or iPad as you lean over them. What about shared lockers or just a coat rack or having no safe place to lock it up if you have an urgent admission and have left it somewhere else? If you're scrubbed in on a surgery or leaving it in your doctor's office while seeing patient, that defeats the purpose of having something so portable. My phone traveled with me everywhere and was big enough to read off of any app, especially "pinching" the area I wanted to see up close. If you have to buy one of those "Inspector Gadget" white coats with 12 pockets for your devices, you're going in the wrong direction. I thought much higher of the Residents and Attendings that had a small amount of stuff on them than those that seemed to carry everything on them, as if they didn't know enough after being a doctor for several years.
More money spent now means less money for UWorld and interviews later when it really counts.