When I was looking for a new tv I first went to the library(Columbus Metro Library) and read what Consumer Reports had on their analysis of the TVs. It was very helpful. If I am recalling correctly I think there was a caution about LCD but I can't remember enough to say here what. They also covered the various things to consider so you can decide which are most important and they have a chart with all the ones tested --which you could make a copy of to take with you.
The other thing is to take a measuement of how far your seating is from the screen. If your chairs/sofa are 3 feet away a 50" is probably too big, and if it is to be wall mounted rather than setting on a stand or table that distance should be accounted for too. I think there may have been recommendations in the article about size and such.