Epson Home Cinema 8100 Projector Screen Recommendations
If you want to lower black levels, then, in general, I'd recommend a high contrast light gray surface, but I'm figuring that many people buying the 8100 over the more expensive 8500UB, are the ones less concerned about black levels. People who are more concerned about sports and general viewing normally aren't focused on black level performance.
Really, though, the screen needs to match three things: The room, owner's viewing preferences, and the projector's characteristics. Overall, in most cases, the room comes first. A high contrast gray screen or a very high power white screen will "reject" side lighting, and can be a great solution to windows without full blackout coverings on side walls, or perhaps an opening into another room on a side wall.
Take all three into consideration. If your room has no ambient lighting issues, and you are strictly a movie watcher, then by all means a high contrast gray, or even a plain matte white should work best. If you have lighting under control, but want as bright as possible for sports, go with a screen with some gain.
Keep in mind that high contrast screens (and, even more so, very high gain screens) have a narrower viewing cone - where you can sit relative to the center of the screen. With a very high gain screen you definitely want to be as close to dead center as possible, and want to avoid being outside of the left or right sides of your screen.
Personally, I've been watching this projector primarily on my Firehawk G3, a high contrast gray (but expensive) screen. It's a very good fit for my room, and my mixed viewing. While in some ways the Firehawk is rather unique, consider screens like Elite's HC gray, and Da-lites HC Cinemavision, as similar type, but less expensive screens.
Home Cinema 8100 vs. Home Cinema 8500UB
This is easy. The Home Cinema 8100 is Epson's entry level projector and the 8500UB is their flagship in the series. For the extra anticipated $1000+ the 8500UB should deliver far superior black levels, a creative frame interpolation system, reportedly siginficantly improved over the older 6500UB. The Home Cinema 8100 is a very good performer, but since the two are inherently very similar, there really isn't anything the 8100 can do better than the 8500UB. Both should be almost identical in brightness.
Ultimately, it is therefore up to your budget and what you are hoping to accomplish. the 8100 makes a really nice projector for the bucks, good in family room or theater. The Epson Home Cinema 8500UB will primarily do much better blacks, but offers a lot of other goodies as well. Both have the same two year warranty with overnight replacement program.
Epson Home Cinema 8100 vs. Mitsubishi HC3800
The Mitsubishi is slightly less expensive than the Epson, or at least that's the case right now, about 3 weeks before both start shipping.
The HC3800 is the more purist projector with excellent skin tones, and that DLP look and feel. The Epson isn't quite as good at that - it doesn't have the same film like quality, but offers far more placement flexibility, like the HC3800 a lot of pop to the image, and a good deal more lumens in brightest mode.
I'm personally hard torn between these two projectors. I'm leaning towards the HC3800 for it's color.Black level performance between the two is comparable. In most scenes the HC3800 comes out slightly ahead or about the same, but on the uncommon scenes that are very dark, with no bright areas at all, the Epson can go blacker. I yearn for the Epson's extra horsepower when needed. No question in two consecutive weeks of viewing, the Mitsubishi just couldn't do as good a job in my room for sports viewing.
I've taken a number of side by side images of these two projectors (so far they are the two best in the mid-$1000 price range). For all of these, the Epson is on the left, the HC3800 on the right:
My usual warnings apply - about trying to read too much into these photos. Too much changes along the path from projected image, to camera - computer - internet - your uncalibrated (and limited in black levels) monitor. (The Epson image is smaller to try to balance the brightness, since the HC3800 is the brighter, in best mode.)
If you are movies only, or primarily movies, aren't rainbow sensitive, and placement issues don't come into play, the HC3800 looks real good. That makes the remaining issue the louder than average fan noise.
If you are sports/HDTV first, or simply aren't quite as critical in terms of image perfection and need the lumens (the Epson's picture quality is very good), then the Epson is likely your better choice. For those of us rainbow sensitve, the Mitsubishi isn't particularly good at minimizing the effect . I find rainbows on the Mitsubishi more frequent than say, the more expensive BenQ W6000, so RBE may be a deciding factor for those who are rainbow sensitive.
Let's compare brightness between the two projectors when in brightest modes. I've got some useful images for you.
The Mitsubishi, at it's brightest really does not have acceptable color way too green, and in that mode, limited control of color. Bringing it down enough to make a real difference requires changing mode from Sports to Standard color's a lot better but lumens are gone.
The first image shows them both at their brightes (Dynamic for Epson, Sports for Mitsubishi):
Epson is on the left
Here are images showing the Epson vs. Mitsubishi, with the Mits doing it's brightest with good color (Standard mode). You can easily see improvement in the first one.
As you can see, there's a big brightness difference favoring the Epson. You should be able to imagine where the Epson, in ambient light could still do a fairly good job, where the HC3800 would be struggling or unacceptable.
What you have here are two serious competitors. Each has strengths, and circumstances that could make it the better choice for you.