LED and LCD are the same, the led part only refers to the type of backlight used to light the screen, typically Led or flourescent Plasma's vary wildly in quality. A top end plasma beats any lcd or led any day and shows more colours and produce's better blacks and is much better for viewing fast moving pictures like sport for example.
But i must admit i do like the slimness of an led.
Yes they are essentially the same, but I prefer the LED over LCD. I ran my old LCD next to my new one and the picture difference was immediately clear. As for Plasma, yes the high end ones are very good, but for my budget at the time the LED was a clear winner for price and picture quality
Choosing a TV is a very personal thing, Something that looks good to me may not look the best to others. You have to go and look at them, and make sure you visit multiple shops to view the same TV as the lighting is different in each one.