I couldn't decide between a plasma and an LCD, so I bought both (with the intention of returning one) and set them up side by side, my cable hookup going to both. The plasma was a Panasonic TC-P42S1, the LCD was a Samsung LN40B630. I did my comparison channel-by-channel with lots of different programming, ranging from talk shows to cartoons to action movies to football games, in both high def and standard def.
Both are very good 40-42 inch TVs, in my opinion. Once I had adjusted the settings to my liking, I was hard-pressed to say that one looked notably better or worse than the other, though each had its strengths and weaknesses.
The Panasonic plasma had slightly more vibrant colors than the Samsung LCD. Blacks were noticably blacker and dark blues and purples looked deeper. The off-angle viewing was fantastic on the plasma, too. With the LCD, a smidge of color was lost when you shifted from 0 to 45 degrees. From deeper side angles, the picture was still watchable, but definitely shifted towards gray.
However, the Samsung LCD had a brighter, crisper image. In a dark room, details stood out better, and any programming that wasn't dark looked a little sharper. During the day, with the sun shining in, the LCD's image held up a bit better, too.
Motion is supposedly better on plasmas, but I couldn't really tell when comparing to a 120Hz LCD. Both TVs did equally well with typical television, and what blurs I saw seemed to be in the source material. I watched a football game for a while, but if the plasma gave a better viewing experience, it wasn't terribly obvious to me. Then again, I'm not a big sports fan, so maybe my eye isn't discerning enough. (Update: see below)
Color accuracy seemed great on both TVs, but the Panasonic needed some adjusting to get there. The picture is too green with the default settings.
Both TVs did a near-equal job with standard def programming (aside from the differences above).
Sound: adequate on both. I have a surround-sound system, so I didn't really care.
Hardware failures: I've read complaints about both brands -- seems like it's a roll of the dice either way. I went with a 4 year warranty.
Other stuff: the Samsung had a better remote, a nicer menu system, and more fine adjustments available. I also like the swivel stand and the fact it's a lot lighter than the Panasonic. I didn't try the internet features on either TV.
Overall, both are very good TVs, and all but the most picky videophiles would be happy with either. In 2009, both plasma and LCD have come a long way and which technology is "better" really boils down to your wallet, viewing conditions, and personal preference. It was a tough choice for me, but, in the end, the bright, crisp picture of the Samsung won out. I can live with marginally less vibrant colors, weaker blacks, and imperfect off-angle viewing (if I watch from the other room, I'll swivel the screen).
*** UPDATE ***
Turns out the Samsung has a demo mode that lets you split the screen and see one half with de-blur processing turned on and one half with it off. I did a little testing by hooking up my laptop and scrolling images and text around. Without the processing, there is a noticeable blur on high-contrast moving objects, though it wasn't significant enough to really bother me. _WITH_ the processing, moving text was more crisp, but there seemed to be a slight delay, which I imagine would make this mode unusable for serious videogamers. People who are highly sensitive to motion blurring might prefer a plasma.Get more detail about
Samsung LN40B630 40-Inch 1080p 120 Hz LCD HDTV with Red Touch of Color.
