Personally, I favor LED (Light Emitting Diode) HDTVs over the other choices. They use far less power, create far less heat, and appear to last a lot longer than Plasma or regular LCD (Liquid Crystal Diode). Technically, an LED HDTV is an LCD HDTV. In TV speak an LED HDTV is an LCD HDTV that uses LED to provide 'back lighting'. TVs labeled as LCD use fluorescent CFL to provide 'back lighting'. Both LED and LCD HDTVs use LCD front panels.
They have improved the technologies to the point that the picture quality in LED HDTVs is every bit as good (or, in some cases, better) than Plasma TVs. As the other Bill pointed out Plasmas still give better 'side viewing than LED, but, since this is for me and my wife, I expect that we will be in front of the TV most of the time.
I found the LED HDTV picture to be sharper and clearer than the plasma equivalent.
LED will cost more than the equivalent plasma by about 20-30%, but, for me the difference will be offset by energy savings over the life of the TV and I like the picture better.
We have a Samsung 55" LED in the living room right now, but, when we move to TV this November on a permanent basis I plan to get a 65", most likely the Samsung 65" Class (64.5" Diag.) LED 8000 Series Smart TV because (among other things) it is the biggest HDTV I can find that will fit into the 60" wide opening in my TV bookcase/console. The 55" will migrate to the 'Man Cave' I'm building in the 3rd bedroom/study -- Iris). I love the built in wireless Internet access to Hulu, etc, and Skype video calling capability (you do have to buy a compatible video camera at about $129) of the TV. It's pricey (roughly $3k atm), but, given the feature set and the amount of time I will probably use the thing it should be worth it to me.