Unless you have a Videophile eye, stay away from Plasma's. They are power hogs, generate a ton of heat, and suffer image burn. Even the new ones to a lesser extent. They look great, but....
I use the high-end Samsung LED monitors in broadcast and production control rooms, and they simply cannot be beat. They are bright, excellent contrast, the codecs look great, excellent viewing angle, etc. Probably somewhere around 50 55"+ Samsung's running 24/7, some with graphics on them the entire time, and we have had zero problems.