LED LCD--Variations and Versions.

[Lavalamp]

There are multiple tvs that use LED's but how they use them is different.
Sony XBR8 and Samsung A950 use LED local dimming. Which means there a bunch of LED groups that can adjust their brightness according to the lighting in the scene. If its a dark scene they only light up in the spaces where backlighting is needed. These are the pinnacle of LCD technology approaching plasma color quality with LCD brightness.
The XBR8 also uses three different color LED's. letting it add more depth to the colors by using colored light to backlight.

The new Samsung 6000 and 7000 series are edge lit LED which means the LED surround the edge of the tv and project light inwards. Making a bright picture but uneven lighting and uneven blacks. Sony also has an edge lit LED but i don't know the series. Samsung and sony will probably release new models with local dimming sometime this summer.

hope this helps.