At 42", go for a Panasonic Viera Plasma. You will not find a single better TV. If you're on a really tight budget, the X series would be quite affordable at that size. If you can manage though the S or G series would be very worthy steps up. The S series adds 1080p. The G series (also 1080p) adds THX certified contrast (its really sweet). Between the G10 and G15 options, the G15 is just a thinner TV, so if you don't need that save $ on the G10.
LCD
( http://en.wikipedia.org/wiki/Liquid_crystal_display_television )
LCDs inherently suffer problems with motion playback. They suffer from motion blur (ghost trails). This is compensated for with the 120Hz/240Hz refresh rates. This feature helps out a lot, but is not 100%. And you are expected to pay a price premium for this add-on.
CCFL LCDs have muted colors, grey blacks, and so-so contrast. This is compensated for with the modern LED LCD. The LED backlight provides a massive jump in quality in regard to those 3 things. It brings it to a near Plasma/CRT/DLP level.
But in smaller sets, LCDs are the go to choice. So for the time being they will certainly still fill an important need there. And there also offer a certain sense of familiarity for many, as LCD computer monitors have been the norm for so long now.
Plasma
( http://en.wikipedia.org/wiki/Plasma_display )
Plasmas are inherently near instantaneous in their refresh rate. They are flawless in motion playback. While you might see some tagged with 480Hz or 600Hz sub-field motion drives, this is not a refresh rate. Its more so marketing to trick consumers (because of LCD's refresh rates). But in reality the technology just works quite differently (its more like your old CRT/tube set).
Plasmas inherently deliver vivid color, true blacks, and deep contrast. They do this right out of the box. They are a better overall image. And so you get a better image and perfect motion playback without having to pay anything extra.
Plasmas were not always this good a choice though, they have improved greatly over the years. But because of those past problems they do currently suffer from many myths and misconceptions. The main ones being that they suffer from burn-in, they are more expensive, they have shorter life spans, and they are energy hogs.
Modern Plasmas do not suffer from burn-in. After they are conditioned, you would have to actually work hard to accomplish a burn-in. To condition a new set all you need to do is keep the brightness and contrast turned way down for the first 100-200 hours of use. After that optimize and enjoy.
Plasmas are not more expensive than LCD rivals anymore. Any especially with LCDs needing high end features like 120Hz and LED backlights to compete. Those features often make LCD far more expensive to buy.
Plasmas do not have shorter life spans. The reputable brands will deliver models that are rated to 60,000 - 100,000 hours. That basically means that in 10 years time, at 8 hours a day, 365 days a year, you would only really see at most about a 10% loss in brightness. So the set is likely well useable for beyond 10 years.
Current Plasma models are now energy star certified. This means no more being power hogs against LCDs. They can match LCDs in this regard. But every model is different. There are some LCDs that still perform better, and there are some LCDs that perform much worse. It changes ever year as new models come out.