Tmobile uses 1900 all over the USA but Would i lose any coverage if my phone has no 850 Mhz? Most of Tmobile phones have 850 Mhz these days.
t-mobile is just in the process of allowing 850 roaming. they have opened a few areas up to 850 roaming, but much more is to follow. If you are satisfied with the current t-mobile footprint/roaming coverage on a 1900 phone, then you can get a 1900 only phone and your coverage would stay the same or get better over time as 1900 carriers build out their network more. a dual band handset would, i nthe future, give you significantly more coverage in some select areas, NJ/NYC not included as bobolito said.