Nokia Lumia 620 vs Nokia Lumia 521

Hello,

My contract with Verizon is ending and I'm moving from a Droid Razr M to T-Mobile prepaid. I was wondering which phone do you think would be better. The 620 is 215 on Amazon and the 521 is 129 on Walmart. The 620 will work on T-Mobile because the 1900 MHz band was reformed in the Atlanta area.