They are both good technologies. DLP is the newer one.
LCD is a 'fixed pixel' display. That means that the number of pixels that make up the picture are always the same. This is only important as you watch different sources from 1080i (HD), 720p (HD), 480p (DVD), 480i (TV). Some may look a little better than others based on the 'native resolution' of the display.
Also if this a projection LCD then you will not be able to get true black because LCD is a panel that light shines through. If you are worried about having the most accurate picture then it may not be for you. I know many people that like projection LCDs just fine and never notice. The true black is not a problem if it is a panel display. A panel display is the thin kind you can hang on the wall like a plasma.
DLP is the latest and greatest. It is not a fixed pixel display and can usually display multiple resolutions. It is a newer technology and has moving parts that the LCD does not have.
I would not worry too much about how they look in the store. They tend to crank up the picture setting so they look good under the bright lights. Once you get a display you should adjust the settings to fit the lighting in your house and save the life of the bulb. Of course this is not as critical for an LCD or DLP because they dont suffer from the danger of 'burn-in' like CRT and plasma displays do.
As for brand I would shop around on the net where there is feed back. There are also several HDTV and home theatre message boards where people have reported problems with different brands.
Hitachi, Toshiba, Mitsubishi, and Samsung I have heard good things about.