Recently someone on a mailing list asked about DLP vs LCD projectors, and since I happen to have some opinions I though I would share.
It’s impossible to say what’s best, and comparisons of high and low end projectors will give vastly different results, but this is based on my experience using a large variety of affordable desktop projectors in the 1000 - 3500 lumen range.

First off ANSI lumens are reasonably comparable between projectors for the most part.

I mean don’t expect two projectors with the same lumen to be the same brightness if they have different lamp hours, and don’t expect two projectors of the same lumen rating but different models to be the same brightness even with new lamps. But ANSI lumens are good enough rating to say that a 2000 will most likely be brighter unless it’s bulb is at >75% of it’s life and than a 1500 is <25% of it's life.

Contrast ratio however is just a mess. There are no standards used to measure this, so different companies will do it different ways, and LCD panels vs LCD projectors vs Plasma displays vs DLP projectors will report such vastly different values that you get the point nothing is really comparable.
DLP claims higher contrast ratio, but LCD counters that it’s only compared to last years models etc. Basically I say you will rarely see it. A) there is no common standard for measuring contrast ratio B) a room at less than 7candels is required to measure at the contrast ratios quoted. C) You must set the projector to “Video” or “Straight” gamma to get that ratio.

Most projectors “standard” and “presentation” gamma bump up the Gama way high to make them appear brighter, and that’s what you normally want in a semi-lit room or for power point or for working with theatrical lighting, retail environments, or daylight. That high gamma is the default on most desktop projectors. But if you are showing a film, or a video installation in a truly dark space you want to switch to the straight Gamma on either type of projector, and you will start to see the contrast.

In most situations I would still choose the higher lumen option over contrast in 95% of cases as the extra brightness may allow you to turn down the gamma, and up the contrast.

Real world experience:
Single Chip DLP tend to have color artifacts, (color aliasing, and color seperation). This will only really show on big subtle and slow moving color fields. (like a landscape, or sky for instance). And you probably can’t see it with a straight video gamma. (it looks like a software color problem, but I’ve seen in on a few brands of DLP?)
A single chip DLP has a color wheel which is spinning Red, Green, Blue, (and sometimes clear and black) color filters in front of the DLP chip at about 300 times a second. This wheel is the most likely thing to break since it is a small fast moving part, and makes this type of DLP less durable. (I’ve only had durability problems with this and BenQ projectors, but it’s a Big problems with those projectors)
Also if you blink fast, or shake your head while looking at a DLP projector you can see the colors separate (try a grid with white lines on black to make this very apparent, and make you feel woozy too)
This temporal color separation is also an issue of you are shooting video of the screen, a camera’s shutter may tend to align with the refresh of the color wheel at times and the image on screen will shift drastically toward Red or Green or Blue. If you set your shutter speed to it’s lowest say 60 this is only occasional and a bit weird. However if you set it to 300-700 it is drastic and you will see disco color shifts on the screen, and still photos may show the same.
On the other hand obviously the refresh rate for the image must be very high so you will not see motion blur, and overall a sharper feel to the image. I personally find single chip DLP projectors a little tiring to watch for long periods of time and attribute this to the refresh.

I actually like my projected image a little fuzzy since the pixels are so big, but making something out of focus is easy to accomplish, and making it sharper if it’s already a fuzzy projection surface is not easy.

LDC will almost always mean 3LCD. This probably makes for better colors than the DLP color wheel, but since there are three there can be alignment problems. LCD projectors tend to be very durable but banging them around for weeks in a truck can dis-align the LCDs. The projectors still work, but you see a little color ghosting.
The LCDs can be re-aligned of course. And most projectors very durable, I haven’t had significant alignment problems since some early 1990 EIKI projectors.
Also due to the alignment or three LCD panels there will tend to be a color wash across the screen from the upper left to lower right, red to green (or maybe it’s magenta to cyan). It’s generally very subtle and you should not be able to perceive it unless you are putting a couple of projectors edge to edge or overlapping them for a blend. In which case you will be putting the most green edge with the most red edge of another projector which will probably be slightly different color and brightness to start with, and it will show. (try swapping them around to minimize this. I also want to try turning one of the projectors upside down next time I encounter this problem, but have not tried that yet.)
LCDs also have a shorter lifespan, so if you are running them 24/7 or even 40hrs a week may be an issue. For most normal projector use it probably won’t matter because you will want a new projector for many other reasons (resolution, brightness, HDMI or whatever is next) before LCD life becomes and issue.

One more note: 3DLP projectors which I’ve only used a couple of times do not have the problems I mentioned for single chip DLP and I don’t know if they pick up any of the problems I mentioned for 3LCD. So far they tend to be super expensive, but very very nice.