Dont buy a verizon iphone 5 cuz it wont work wit tmobile it will work only on 3g and 4g but not 4g lte buy the one from at&t cuz that one will work good and buy the 1428
Since T-Mobile has no LTE network at this point and wont for about another 8-12 months, it really doesn't matter too much.
Either one should get T-Mobiles HSPA+ 42 if you are in an area that has been refarmed for it.
Since I made my post a few hours ago, I found a white AT&T unlocked iPhone 5 on Craigslist and have already bought it.
I have been told by T-Mobile that only the iPhone 5 will get HSPA+ speeds. Every other gen will get 3g speeds, which are very good btw.