I went for LCD
Personally, I bought a 40" LCD. I compared several LCDs and several plasmas but ultimately went for a very good Samsung LCD and haven't regretted it at all. What you need to consider is that LCDs tend to have better resolution for less money. That's starting to change but slowly. Plasmas tend to have better black and contrast levels. Generally speaking, the contrast and black levels make a bigger difference to perceived image quality than resolution. That depends on the size of the screen and how close you're going to sit to it. It's also hard to judge these things in the store because of the amount and quality of the lights there - plus the set-up of the screen.
I went for the Samsung F series and, side-by side with a good plasma there's little difference in terms of image quality and stability. The plasmas have slightly better contrast. Basically, I would summarise as: if you're going for a cheap fairly large display go LCD with a high resolution. If you're prepared to spend a lot of money then go for a high resolution (1080p)plasma. It's the medium price level that's the difficult choice. I'd say pick a few models of each in your price bracket and try to see them in a showroom side by side. It won't be a definitive answer, due to the store conditions, but should give you an idea of which way to go. Look particularly for motion blur and reaction time. I saw speed2 the other day and, although a generally poor movie, there is a sequence where they're in a room and the lights flick on and off. That sort of thing really shows up response time and motion blur.