I would go with DLP. Sony has an awesome new setup with their SXRD technology which has twice as many pixels as a normal HDTV.
First of all we are talking about 3 different technologies ... not 2.
Plasma, DLP and LCD, the last 2 being of micro-projection variety. The Sony boxes are LCD, not DLP. Their new SXRD is a hybrid of LCD technology. I'll deal with the 2 technologies you are asking about ... DLP vs Plasma.
Plasma screen enjoy an advantage in a wide range of categories including clarity, saturation, brightness, etc. It's also a smaller package at almost any screen size (thinner/smaller). DLPs are becoming thinner though and you will see models that can mount directly on the wall in the near future. As with all things the image quality is dependant upon the source. (Cable, antenna, satelite, DVD, VCR, etc.). Great video sources will look pretty damn good on either technology.
Plasmas have an almost perfect 180° viewing range. DLPs and LCDs are good, but not THAT good.
DLP generally uses less electricity to run a screen of the same size.
DPL will be available soon in sizes up to 84 inches! Plasma is currently maxed out at 61 (IIRC).
DLP is less expensive than plasma.
DLPs are NOT affected by altitude. Plasma (gas in a tube) will have problems and consume more energy as altitude goes up. Serious problems occur at 6500 feet.
DLPs do in FACT have a longer lifespan than Plasma. DLP is a 'light and mirror' technology. Once the bulb burns out (80,000 hours average), simply replace it ($200) and start another 80,000 hours. Plasma, by contrast, uses a small electric pulse for each pixel to excite the rare natural gases argon, neon, and xenon to produce the color information and light. As electrons excite the phosphors, oxygen atoms dissipate. These rare gases actually have a life and fade over time (60,000 hours average) The life of the plasma display itself is usually determined by half-life of the phosphors. So at 30,000 hours the phosphors will be at their half-life, and the viewer will be seeing an image that has half the brightness capability. At this point the TV is on it's last legs. The gases in plasma TVs cannot be replaced.
DLPs do have one major drawback. The DLP 'rainbow effect' is an artifact unique to single-chip DLP projectors. The artifact appears as a rainbow or multi-color shimmer briefly noticeable when changing focus from one part of the projector screen to another. It appears as a secondary image that appears at the viewer's peripheral vision and is generally noticeable when shifting focus from a high contrast area or bright object. This effect is NOT noticed by all viewers. I believe the percentage quoted was less than 10% of viewers. The newer 3-chip DLP projectors, higher wheel speeds, 7-segment color wheels, and new color wheel designs are minimizing or may altogether elminate the effect.
In short, if money isn't really the object I'd go with plasma. The picture is generally better across a wide variety of video input. If cost is an issue and you would be happy with a very good picture (but not the best thing available) go with DLP. Having said all that ... I went with a 50" Sony LCD.
They are the ONLY manufacturer I would consider for LCD technology. Their picture was every bit as good (if not better) than ANY DLP screen. There are of course pros and cons with LCD technology as well ... but we'll save that for a different day.
PS exhawg is correct in one critical aspect. CRT televisions STILL rate out with the best picture quality. But that difference in quality is closing fast. The down side to CRT technology? 36" is the maximum screen size available AND it's a pretty big box.
