Plasma vs LCD or LED which would be best?

I'm going to renovating a room into an entertainment center that will be dimly lit so Plasma seems to be the way to go but do certain Plasma T.V.'s dim or darken when you move around the room and you are not sitting in front of the television? Also are there any LCD or LCD/LED televisions that do not have screens that darken when you are not sitting directly in front of the television? What kinds of television does not have that darkening effect when you don't sit directly on front? I'm looking for a television that is 42' to 50' if that helps.

Suggestion:

Ideally an LCD TV is best for your application. LED TVs are just LCD TVs with a different kind of backlight (leds and not flourescent lamps), so they can create richer colours and deeper blacks. There are too many issues with plasma, screen burn in for example and low lifespan.

A good LCD TV with good contrast ratio (eg SAMSUNG, SONY, PHILIPS, PANASONIC) would be your best bet imo.

Good luck.