I just went through the angst of LCD versus plasma a couple of months ago. There's lots of information on the AV forums on this type of thing.
They both have their unique advantages. The advantages of plasma are being eroded by LCD more quickly than the advantages of LCD are being eroded by plasma.
First, unlike LCD, the plasmas are subject to burn in, no matter what the marketing people tell you. They're working on it, but it still could be an issue when you have station logos constantly displayed on the screen. It could also be issue if you watch something broadcast in 4:3 on a 16:9 screen and have black bars on the side of the screen. You could stretch the picture of course, but I don't like the distortion it causes. The black bars could also cause screen brightness to fade unevenly with time. Advantage to LCD on the burn in issue.
Second, LCD should last longer. Plasmas run hotter which will shorten their life considerably. They use less power too. And when you see specs saying 20,000 hours of life, and so on, take it with a grain of salt. You'll notice brightness drop off long before that. Advantage to LCD again.
Third, off-axis viewing angle is no longer an issue with LCD. That advantage which plasma had over LCD is gone. I call this one a draw.
Fourth, plasma screens will reflect glare and images. You have to be careful with placement and lighting or you'll be looking at reflected images of objects in the room. Advantage to LCD.
Fifth, sixth and seventh: colour saturation, contrast ratio, response speed are all to plasma's advantage over LCD (and to CRT's advantage over plasma). I was very concerned about these points when I initially went shopping. However, after seeing the current generation of LCD, I no longer felt it was a significant advantage to plasma. As long as you don't cheap out and buy a budget brand, LCD is very good on these points. I watch a lot of sports with fast moving balls and pucks. Once you get below about 8-10 ms in response time, fast moving objects like balls no longer have a comet tail as in earlier LCDs. In my view, although plasma does have better specs on these points, LCD has closed the gap to the point that it is no longer an advantage for plasma. Same with colour depth or black/white contrast. Advantage to plasma on these points though.
Eighth, and to me this was very important: pixel size. LCDs have smaller pixels. You will get sharper clearer pictures as a result. If you are going to go into high definition, this is a significant advantage for LCD, and plasma is not closing the gap on this point to any significant extent at this point in time. Advantage to LCD.
There is another effect caused by plasma's larger pixels. You have probably heard of the "screen door effect". Looking at a plasma screen is like looking at the picture through a screen door. You see the grid caused by the spaces between the pixels. Early LCDs were very bad for this, but it is now virtually non-existent for LCD. Not so for plasma. When I'm walking through a store, I can spot the plasma grid from twenty feet away. It's the type of thing that once you notice it, you always notice it. I find it incredibly annoying. Advantage to LCD.
Once I satisfied myself that LCD was fine for response speed, colour depth, and contrast, the sharper detail in LCDs due to the smaller pixel size, and the lack of an annoying screen door effect, made LCD a clear, unequivocal winner over plasma in my purchase decision.
Use your own eyes to see which you prefer, plasma or LCD. Whichever one you choose, remember that you get what you pay for. Avoid the budget brands. I found the budget brands to have noticeably inferior pictures. Stick with brands like Pioneer, Panasonic, Samsung, Sony, Toshiba. I ended up with a Sony LCD, but I was very impressed with the Panasonic LCDs as well.
I wouldn't bother with DLP. No rear projection is as good as a direct view TV. DLP is a very good technology, but I don't think it will ever be developed to its full potential. I don't think the market wants it, especially now that plasma and LCD are dropping in price and evolving in operformance at the rate at which they are.
On the point of price. "Cheap" plasmas are not expensive but, as noted, you get what you pay for. "Good" plasmas are still expensive. They are still less than the price of LCDs though if you're looking at large screens. Advantage to plasma on this point.
Now if you can hold off for a year, wait until you see the new SED TV's. If these things are priced competitively when they come to market, plasma and LCD will both go the way of eight track cassettes. Well,... LCD will hang around for specialized applications like laptops, small TV's and cell phone/PDA screens. Plasma will be in the garbage can of history though. I think of plasma as being more of a transition technology and not likely to be around for the long haul. Not that it matters for your purchase decision today.
Anyway, that's my opinion, for what it's worth. Enjoy yourself looking for your new TV. It's always fun to go shopping for toys.
They both have their unique advantages. The advantages of plasma are being eroded by LCD more quickly than the advantages of LCD are being eroded by plasma.
First, unlike LCD, the plasmas are subject to burn in, no matter what the marketing people tell you. They're working on it, but it still could be an issue when you have station logos constantly displayed on the screen. It could also be issue if you watch something broadcast in 4:3 on a 16:9 screen and have black bars on the side of the screen. You could stretch the picture of course, but I don't like the distortion it causes. The black bars could also cause screen brightness to fade unevenly with time. Advantage to LCD on the burn in issue.
Second, LCD should last longer. Plasmas run hotter which will shorten their life considerably. They use less power too. And when you see specs saying 20,000 hours of life, and so on, take it with a grain of salt. You'll notice brightness drop off long before that. Advantage to LCD again.
Third, off-axis viewing angle is no longer an issue with LCD. That advantage which plasma had over LCD is gone. I call this one a draw.
Fourth, plasma screens will reflect glare and images. You have to be careful with placement and lighting or you'll be looking at reflected images of objects in the room. Advantage to LCD.
Fifth, sixth and seventh: colour saturation, contrast ratio, response speed are all to plasma's advantage over LCD (and to CRT's advantage over plasma). I was very concerned about these points when I initially went shopping. However, after seeing the current generation of LCD, I no longer felt it was a significant advantage to plasma. As long as you don't cheap out and buy a budget brand, LCD is very good on these points. I watch a lot of sports with fast moving balls and pucks. Once you get below about 8-10 ms in response time, fast moving objects like balls no longer have a comet tail as in earlier LCDs. In my view, although plasma does have better specs on these points, LCD has closed the gap to the point that it is no longer an advantage for plasma. Same with colour depth or black/white contrast. Advantage to plasma on these points though.
Eighth, and to me this was very important: pixel size. LCDs have smaller pixels. You will get sharper clearer pictures as a result. If you are going to go into high definition, this is a significant advantage for LCD, and plasma is not closing the gap on this point to any significant extent at this point in time. Advantage to LCD.
There is another effect caused by plasma's larger pixels. You have probably heard of the "screen door effect". Looking at a plasma screen is like looking at the picture through a screen door. You see the grid caused by the spaces between the pixels. Early LCDs were very bad for this, but it is now virtually non-existent for LCD. Not so for plasma. When I'm walking through a store, I can spot the plasma grid from twenty feet away. It's the type of thing that once you notice it, you always notice it. I find it incredibly annoying. Advantage to LCD.
Once I satisfied myself that LCD was fine for response speed, colour depth, and contrast, the sharper detail in LCDs due to the smaller pixel size, and the lack of an annoying screen door effect, made LCD a clear, unequivocal winner over plasma in my purchase decision.
Use your own eyes to see which you prefer, plasma or LCD. Whichever one you choose, remember that you get what you pay for. Avoid the budget brands. I found the budget brands to have noticeably inferior pictures. Stick with brands like Pioneer, Panasonic, Samsung, Sony, Toshiba. I ended up with a Sony LCD, but I was very impressed with the Panasonic LCDs as well.
I wouldn't bother with DLP. No rear projection is as good as a direct view TV. DLP is a very good technology, but I don't think it will ever be developed to its full potential. I don't think the market wants it, especially now that plasma and LCD are dropping in price and evolving in operformance at the rate at which they are.
On the point of price. "Cheap" plasmas are not expensive but, as noted, you get what you pay for. "Good" plasmas are still expensive. They are still less than the price of LCDs though if you're looking at large screens. Advantage to plasma on this point.
Now if you can hold off for a year, wait until you see the new SED TV's. If these things are priced competitively when they come to market, plasma and LCD will both go the way of eight track cassettes. Well,... LCD will hang around for specialized applications like laptops, small TV's and cell phone/PDA screens. Plasma will be in the garbage can of history though. I think of plasma as being more of a transition technology and not likely to be around for the long haul. Not that it matters for your purchase decision today.
Anyway, that's my opinion, for what it's worth. Enjoy yourself looking for your new TV. It's always fun to go shopping for toys.