For those with smaller screens, the Mitsubishi lamp life, in low power mode, is even better than the Epson's: 5000 hours vs. 4000 hours. This is probably due to the larger than normal drop in brightness of the HC5500 (26%) when switching to low lamp mode. The Epson though, is rated 4000 hours in full lamp power, twice that of the Mitsubishi. It is my belief (based on feedback), that most projector owners tend to run in full power, and if you buy into that assumption, the Epson has the advantage for most buyers, in terms of cost of operation.
The HC5500 does a pretty good job in terms of those "all important" black levels, for an entry level 1080p projector. The Epson does as well, however, and we give it a slight advantage in this area. They are close, however, and, put another way, they are almost identical to each other, relative to comparing the 6100 with any of the "ultra high contrast" 1080p projectors, including Epson's own 6500UB, the Mitsubishi HC7000 and the Sanyo PLV-Z3000! The difference in terms of black level performance between these two, is not likely to sway you one way or another, other factors will be far more significant!
One of the biggest differences between the projectors is placement flexibility. You can't beat the Epson at this, with lots of lens shift, and a 2.1:1 zoom. By comparison, this Mitsubishi projector (unlike their more expensive HC6500 and HC7000), has very limited zoom - only 1.2:1 - and a bit more limited lens shift. Because of the limited zoom, the HC5500 won't work shelf mounted, in a lot of people's rooms, as for a 100" screen, the furthest back it can be placed is only 12.8 feet (compared to the Epson's just over 20 feet). That makes the Mitsubishi a ceiling mounted projector in most rooms.
Shadow detail on both Mitsubishi's and the Epson is very good, but not the best. It's a close call, but I'll give a slight edge to the two Mitsubishi projectors over the Epson.
Sharpness: Close enough to not matter, both produce a very nicely sharp image.
Warranty: Epson and Mitsubishi both provide 2 years parts and labor, but Epson wins for offering their overnight replacement program for both years. If you have a warranty problem with the Mitsubishi projectors, you'll have to send it in, and suffer downtime waiting for repair and return.
The Mitsubishi HC6500, in general performance, closely resembles the HC5500, most notably in brightness and black level performance. The big difference between the two Mitsubishi projectors is in two areas:
First, is pricing! While the HC5500 is typically less expensive than the Epson Home Cinema 6100, the HC6500 is a few hundred more than the Epson (US pricing).
The second difference is in placement flexibility. The HC6500 has a zoom lens with more range, allowing it to be placed as far back as 16 feet, five inches. That's still not a match for the Epson's 20 feet and change, but enough to allow many to shelf mount the Mitsubishi HC6500 in the back of their rooms. Still, a significant number of owners will not be able to place the projector far enough back and will still have to ceiling mount.
As mentioned above, the HC6500 is about the same in black level performance as the HC5500 and therefore the Epson as well, but, again, with the Epson having a slight advantage.
Both Mitsubishi projectors are extremely quiet, compared to the Epson's slightly noisier than average performance in terms of audible noise. That may well be a deciding factor for a number of shoppers.
The Epson is a decent looking "box" in terms of physical styling. That puts it on par with the HC5500, but the HC6500 is a particularly attractive projector, physically. It definitely wins in terms of looks - although most of us are more concerned with image performance. Still, the black HC6500 will help with the wife factor, compared to the white finished, plain looking Epson.
Bottom line: The Epson has a significant advantage in brightness when you need one of those "brightest" modes for viewing, and that's probably the biggest single advantage. Placement flexibility may come into play, especially comparing the HC5500 to the Epson 6100, but less so with the HC6500. Much lower audible noise, however, significantly favors either Mitsubishi. The HC5500 also has the pricing advantage, whereas the HC6500 costs more than the Epson. Sharpness differences are not a factor, nor, should shadow detail be one, although the Mitsubishi's are a touch better than the Epson at shadow detail.