Depending on how close you are (I assume you'll be on your bed.) with anything under 30" you won't notice a difference between 720p, 1080i, or 1080p. With a TV that size more than 6' away your eyes just can't pick up the difference.
I'd recommend getting a 720p/1080i with the highest contrast ratio and lowest response time you can afford and make sure to look at it before you buy. Watch it until you know how you feel about how colors are displayed. Brightness is slightly less important since bedrooms are usually heavily lit.
TVs in the size and class range you're looking at vary widely in quality. Pic the one you like best that has the features you need.