As far as pq, the plasma is going to be better. I'd even go so far as to say a 720p plasma will look better than a 1080p LCD. I've got a Samsung 5044 720p 50" plasma that looks stunning. My 46" Aquos 1080p has a very, very good picture and is great in a brightly lit room. There are disadvantages though, to both. Here are a few I see with my sets:
Plasma:
1) You should run the break in DVD for 250 hours to harden up the pixels. That's a pain in the neck, but a necessary evil many recommend. The first few hundred hours are when the pixels burn their brightest, so be forewarned. I did it with mine, and run a pretty high contrast and sharpness level, with no ill effects of IR or burn in. Others haven't been so lucky. Don't question it, just do it.
2) You have to be careful about "torch mode" even after the break in period. So many people have logos burned into their plasma's because they've taken full advantage of the outstanding contrast levels on these sets. Do not run a plasma in "torch mode", aka dynamic mode with a logo or ticker running for more than 15 minutes. Image retention can turn to burn in quickly when a static image is displayed for hours upon hours. This can be an issue for sports fans who watch a lot of ESPN. You can tone down the contrast/brightness levels, but it defeats the purpose of why you bought plasma in the first place.
3) Most plasmas have a "buzz" that drives people nuts. My Samsung is silent, but I know the Pioneers have it. Some worse than others. Make sure you demo these sets before purchasing and can live with that slight buzz.
4) Weight. These things are heavy. Twice as heavy as a similar sized LCD. If access to the back of the set is difficult, an LCD would be easier to turn.
5) Heat. Plasma's put out a lot of heat compared to LCD's. They also consume twice the electricity. Keep it well ventilated.
6) High elevation. If you live in extremely high elevations, don't buy a plasma.
Here's two owner reviews on Pioneer's latest and greatest 50" Elite Pro 110FD Kuro:
www.amazon.com/review/product/B000W3I0UM/ref=dp_top_cm_cr_acr_txt?_encoding=UTF8&showViewpoints=1
LCD:
1) Soft picture. After looking at a properly set up plasma, you'll say your LCD is a bit softer. With BD and HD DVD, I can get away with high contrast and sharpness levels and no digital noise reduction for a pristine picture, but need to back it down on sd feeds. Most 720p plasma's have better pictures than the newest 1080p LCD's when properly set up.
2) Motion blur. Every LCD has it. Even mine at 4ms. If you want a razor sharp picture without DNR, expect pixelation and motion blur. It's horrible with basketball. But, turn on the DNR or fast motion setting, and it all but disappears (as does the crisp picture). This is the biggest downfall regarding LCD's - especially if you're a sports fanatic.
3) Color banding. This is more of an issue with the Aquos LCD line, but I can see it on my Acer PC monitor, Dell laptop, Olevia LCD, so I think it's more prone to LCD's than plasma's. It's not a big issue. You may see it less than 1% of the time, but when you see it, you'll know. Certain colors don't fade smoothly on a bright background.
4) Black levels. Some of the newer sets have outstanding black levels. My Aquos is excellent, but still "gray" in comparison to my plasma. If you don't compare the two side by side, it's not an issue. But when you do, you'll pick the plasma. Excellent black levels make a flat screen, and plasma trounces LCD in this area.
