What's best is in the eye of the beholder unfortunately. Once you get used to the brightness of an lcd or led, plasmas look dull and poor. I've had 4 lcd's and was sure after trawling through av forums, a panasonic 46" plasma was going to be my next tv. However, after buying one i just couldn't get used to the dullness of the picture. When i went back to the shop, the guy said that people just have different views on what looks best. Once you get used to one thing, that's what you like
Ref LED's, there is actually very little between lcds and leds. Energy saving and thinness is the main difference. Samsung cheat a little bit. All their leds have the ultra clear panel which is basically a shiny clear panel that makes the screen look really black in dark scenes and makes all other tv's look like they have a grey panel blocking/dulling the picture. If you check out their high end lcds, they have the same ultra clear panel and if anything, the picture looks even better. The very brightest colours look slighly more natural and crucially you get that ultra clear panel which gives the wow factor.
Look at LG and sony leds, they look no different at all to their normal lcds, some of the lgs incredibly dull.
Ignore all the opinions here and go to your local currys (hopefully a refurbed one with all the nice displays in HD) and decide what looks best in your eyes.
Try to get 100hz, def get 1080p, after that decide what works for you