Hey there, long time lurker, recent recruit here,
I've sold tvs for a rather long time, so I can definitely give you some insight on plasmas. I also install them (ie wall mounting, setup and the like)
I prefer plasma personally. Better colour, better motion, and longevity is equal to or better than lcd according to Samsung or Panasonic with 100,000 hours of life as standard.
Burn in is only an issue if you are being purposefully cruel to the tv such as leaving a game on pause for a couple of days or a week. But as was mentioned before, beware of cheap brands. Oh and the first 100-200 hours of using it. Play games, watch movies but turn it off if you need to leave the room...
People get burn in and image retention confused. Plasmas will sometimes have a ghost image of something that was on screen for a prolonged period of time such as a speedometer or hud of some sort, but it goes away after 5-10 minutes of watching something else.
The older the plasma tv, the better proof against burn in it is. I've been gaming on my 50" S1 series Panasonic and have yet to experience anything other than temporary image retention. The anti burn in tech is really not needed but they put it in the menus so people can have peace of mind. It usually works by orbiting pixels in a pattern too minute to detect with a human eye at 8 or more feet away. It works but not really needed.
The only real drawback with 120hz lcd/led tech is it creates frames that do not exist in the source material. This is where you get odd blurring or shimmering around moving objects on screen. Plasma doesn't suffer from that because it's capable of updating much more quickly than 120hz or even 240hz. Don't take this as a knock against lcd/led, because each form of display has it's distinct advantages.
Panasonic VT25 series has some of the best colour reproduction period. Not even LED can come close to the black levels and contrast ratio. It's a 3d tv, but ironically, everything that makes it a great 3d tv, makes it a phenomenal 2d tv.
Same with the 3d Samsung plasma/LED or Sony LCD/LED tvs. Better processors make for better image quality for everything.