Generally the tv's specs will list if its 1080p ot 720p. Honestly, go with 1080p is you can swing it. Contrast ratio has something to do mwith how bright the tv can get - i'm not 100% clear on it but i know a/v dorks get all squishy when a tv has a big contrast ratio.
I just recently picked up a 42in sharp aquos, and am totally loving it (as is my ps3)