Both projectors measure between 1000 and 1100 lumens in brightest mode, so again, no clear winner.
Some folks prefer DLP projectors, over all, for the film-like qualities, although I didn't find the HD80/HD8000 series to be exceptional in that area. I think buyers will favor one over the other, based on their personal preference for DLP or 3LCD images. The Optoma, I should note, is always particularly good at having rich dark colors that standout. Both have about the same zoom lens attributes, but the lens shift will allow some to shelf mount the Mitsubishi, which may be a deciding factor. This is more of an Apples vs. Oranges, than a better/worse comparison. That makes it a tough call.
Mitsubishi HC5500 vs. BenQ W5000
Now here is a real competition. We start with the basic differences between 3LCD and DLP, add to that, that the BenQ W5000 really has very good color handling, and both have similar physical attributes (limited zoom, and about the same lens shift).
Brightness is about a wash. The manual iris on the BenQ, depending on how you set it, lets the BenQ W5000 straddle the HC5500 in brightness. With the iris almost closed, the BenQ W5000 produces 472 lumens, but open, 670 lumens in "best mode" (Cinema).
In brightest mode, the BenQ, depending on whether you are using Brilliant Color, can produce from 755 lumens to 1270. I don't recommend Brilliant Color for movie watching - it does degrade image quality, but for HDTV/Sports, when you need the lumens, it comes in handy. Over all, therefore, the two projectors are pretty similar in brightness, but the W5000 can muster up about 20% more lumens if needed, but it won't look as good as the Mitsubishi at its brightest.
The BenQ W5000's post calibration picture quality is excellent, and I'll give it the advantage over the HC5500, including being more film-like for movie watching. Both are extremely sharp, so no difference there. The BenQ suffers from more image noise than any other 1080p projector reviewed, but, supposedly BenQ is working on a firmware fix (it's been 5 months now?).
Bottom line, tough call. My own personal choice would be the BenQ, overall. (But, I admit to previously owning 2 BenQ home theater projectors - the last one being the PE8720), before I jumped to 1080p and the JVC DLA-RS1, so I may have some bias. The BenQ image is simply more impressive over all, despite the image noise problem!
OK, that covers enough of the competition, especially since several of the ones mentioned will be replaced in the next 2-4 months with newer models.