I'm of two minds.
I'm considering a long hike and the 11 inch would pack light, but if you use a computer a lot, the bigger screen is nice and I would even be considering a
15" Mac Book Pro.
I am currently using a
27 inch i-Mac and I LOVE the large screen.
But it's NOT portable, so I'm considering an
iPad for portability, but I'd miss the keyboard.
It really DOES depend on HOW you're going to use it, as to which one to buy.
I don't know if you have friends who have an Apple, but go to a store and try playing with them for a few minutes.
If you have a military friend, have him take you to the Base Exchange and get the sales person to explain the differences and allow you to put your hands on them and play with them for a few minutes.
An Apple store is also an option, but you don't have to buy when you're just looking and learning.
You can buy off the internet just as well and probably cheaper.
Don't forget to checkout the
Refurbished & Clearance from Apple, because their warranty is just as good as a new one.