Sony Ericsson T610

Ok. Well I am currently a Nextel user and i hate it. My plan ends next week and i feel in love with the Sony Ericsson T616 and th T610. I found out that they are the same phone only one works with At&T and the other for T-Mobile. I live in Westchester, NY, and i would like to know if anybody knows if T-Mobile or At&T has better service in my area....reply back or e-mail me at [email protected] with a big subject so i can see it in all the junk mail....Thanx