Plasmas suck and are overrated...
Actually, I can tell you how it used to be when I was in college, because we used to have long discussions about them. I don't know if things have changed:
Plasma Pros:
Excellent picture quality, supposedly the best you can get
Highly promoted, and very limited quantity available
Most have multiple inputs, which programmed properly can allow multiple PinP's, etc.
Cons:
Often warrantied for 10 years, but gas is known to leak out, and will be Black and white for 8 of the 10 years. But they still work, so this doesn't fall under the warranty.
Overpriced from the get-go. For what you can get a plasma for, you can get a higher quality LCD.
You still have to buy all mounting hardware, and if you're going digital, often a digital tuner too...
Very sensitive to bumps, drops, etc.
Very sensitive to irritants to the gas, although I don't remember what they are...
LCD Pros:
Supposedly will last far longer than the old "Tube" tv's
Superior picture, some even say to Plasma
Best quality for the money invested
LCD Cons:
You still have to buy all mounting hardware, and if you're going digital, often a digital tuner too...
That's all I can think of off hand. Ultimately, (at least back then), LCD's were the #1 choice for professionals (I'm in the television production business, so this is important for me) as far as longevity and quality. The station I work for as 5 or 6 plasma's, and they've experienced multiple problems that are VERY expensive to fix. Granted, they are early generation tv's, so bugs may have been worked out since then. There used to be a 98% fail rate on Plasma screen production, which is part of the reason they were so expensive. This means for every 100 screens produced, only 2 actually worked...
My next TV is going to be an LCD, hands down...