Older plasma models are much more prone to burn-in. There have been great strides in the technology and the newer plasmas - Panasonic Viera, Pioneer KURO, Pioneer Elite - are phenomenal and available in 1080p.
I believe Pioneer offers the KURO - which is literally the best plasma on the market, beats any screen in any comparison - is the only one with an LED backlighting. Or, it could be the Elite series.
Plasmas are far better as far as color reproduction; images appear more like film (i.e. real) whereas most LCDs are overly saturated with their color palette. Also, what sucks about LCDs unless you get a very top end model is that their color fidelity is NOT uniform. You can stand in the center of the screen and gradually walk to the side while still looking at the screen, and you will notice a color shift.
This does not happen on all models but LCDs are notorious for this.
Think of what this means for viewing. Unless you are dead center, the colors may not be the same as they appear if you were viewing the screen dead on.
Now, with regards to LED, you want to see the phrase "local dimming" which means the LEDs are lighting the screen from behind each pixel (it won't be one LED to one pixel, but with an LED focused behind a set of pixels the LED light output can be controlled more tightly, thus giving better contrast range, deeper blacks and whiter whites).
Currently, most LED LCD panels use LED lighting from the edges of the screen.
The Samsung Series 9 LCDs have local dimming LEDs. The 8500 series might as well but I'm not sure. I think Sony makes an LCD with locally dimming LEDs but I forget the model.