Resolution is the big one (480i, 480p, 720p, 1080i, 1080p). But, don't forget to look at what type of video inputs are available on the tv. Make sure its got at least 1 HDMI input, preferably 2. This is really going to come down to what your sources are i.e. DVD player, Cable Box, Satellite Box, XBOX/PS2..etc.