I do this for a living (wholesaler). No offense, but Moviemaster is wrong and everyone else is pretty much correct. Nice job KC, Post, and JC.
I have an lg plasma. LG makes the Zenith. It is their lower end no frills line. good bang for the buck. I was watching all three Lord of the Rings over Thanksgiving weekend and I noticed some burn in with the Encore symbol. Think of it like a wipe board. Just play something with motion and it will go away and away it did.
Like others said, plasma is hotter and uses more juice. It also reflects light more, so if you are in a very bright room get an LCD or LED.
Picture quality is better on plasmas. Look at the facts. Plasma is 600hz. LED are as high as 240, but most low end are 60hz or 120hz. The hz refers to the refresh rate. So if you watch a lot of action movies or play games, you will get less quality with an LED or LCD. You will notice that many LEDs have gaming mode. That is to help correct the refresh rate issue, so your games look better. Plasmas do not need that at all.
In a size such as a 42 inch it does not matter so much. Just make sure it is 1080p not 720p and if pos get 120hz. Go by price and it won't matter. When you get up to 50, 60 or larger you will want a much better set. Non hd stuff looks like shit on any tv when you blow it up to 60 inches (i have a 60) and that is not the tv that is the content. I would not buy the Zenith, but if it is such a good deal, youy prob cant go wrong. But trust me on a small 42 inch size it does not matter so much.