NEW Plasmas in general have a 35,000-60,000 hours hour life span depending on the brand and model. LCD's lifespan is comperable, maybe 10% more on the highest estimates for longevity. The "Plasma TVs don't hold up" thing is from the oringinal models in 1999-2001 which were crap for the most part. That is no longer the norm.
LCDs are better for gaming only because they have virtually no chance of burn-in. Plasma, though nowhere neare as likely to burn in as most people think, does have a chance to burn in.
Which looks better? When looking at them head on (no angle) the good LCDs and the good plasmas look nearly identical. The only way one can tell an LCD is by the latency. The LCDs tend to have more aliasing (get blocky on the edges of a fast moving object - very, very subtle..) because the LCD pixel takes much more time to switch from one state to another than a plasma pixel. So when watching football or a fast chase scene in a movie, the LCD tends to get blurry in comparison to a plasma. again this is VERY slight.
The better LCDs can be viewed from just about any angle, but there is always some brightness and contrast difference between head-on viewing and angled viewing. This is because there is a light shining though the LCD panel and that is how the picture is made. The plasma's picture is made up of glowing nodules of gas/plasma so no matter what angle you look at it, the glowing plasma is the same brightnes and hue.
Plasmas in general have blacker blacks than LCD. The reason is that LCDs make black by blocking the light shining though the LCD panel. Plasmas just don't activate those pixels at all so the blacks are much purer. Again, the better LCDs make very dark blacks. 7.5% luminance is considered a good "black level" anyway.
LCD panels are cheaper to make in the smaller sizes than plasma. But when you get to anything over 32-35" then the plasmas are much cheaper only because they are cheaper to make. Economies of scale also play into this. But LCDs in larger sizes aren't necessarily more expensive because they are better.
How do I know this? I own one of each! I have a 32" LCD (Toshiba 32HL66) and a 42" Plasma (Hitachi - Forgot the model number off the top of my head) I've seen it with my own eyes.
Both sets provide a great picture and are good in their own way. I like the look of the plasma better, but this is a PERSONAL POV and it could change as technology moves on.
If you want to confuse yourself further, take a looks at this page and follow the link to "plasma vs LCD" too.
http://www.plasmatvbuyingguide.com/plasmatv/plasmatv-lifespan.html
---This article is newer and maybe a little more objective
http://www.cnet.com.au/tvs/0,239035250,240036500,00.htm
Oh...one more thing.... The luminance and contrast numbers, IGNORE THEM!!!!! Unless you are comparing models from the same brand, these numbers have absolutely no commonality. There is no standard what-so-ever. Manufactures litterally make them up! They come up with whatever test to come up with the highest or coolest sounding number they can publish.
No matter what you do MAKE SURE YOU LOOK AT THE TV WITH YOUR OWN TWO EYES before you buy one. NEVER EVER go by specs. I was about to buy a different Hitachi model Plasma than I ended up buying because the numbers looked good on paper. That model had the worst looking picture of all the sets I looked at that day even after tweaking the picture on three different TVs of the same model. I did this at several different stores. I ended up with a different, model which ended up costing LESS.
See ya
Tony
I know that this is a hot-button for some RP folks, but there is no doubt that a 6 year-old well used RP set has a yellower screen than a brand new one. Why is this important? It changes the color balance off for EVERYTHING. The change is very gradual and not noticeable to the owner of the set that looks at it every day. But to an outsider an older RP will look washed out and ...well... yellow. 
