Again, this is based on the RS1's performance, not the RS1x. However, I would expect the two to be similar.
The JVC RS1x (based on that assumption) is about as good as it gets out of the box. That's a good thing, since the older RS1 had very limited color management controls. I'll go as far to say, that it offers less than any other 1080p projector.
The Epson Home Cinema 1080 UB (and the Pro Cinema 1080 UB), by comparison is more of a mixed bag. Epson's primary "best" mode, is Theatre Black 1, and it is very good out of the box, but not the exceptional color balance of the JVC DLA-RS1 (and hopefully the RS1x) when you first turn it on.
The JVC has only three modes, compared to seven for the Epson. All three JVC modes are at least very good. That's definitely not true for a few of the Epson modes. Most significantly when you need a brighter mode than Theatre Black 1, then Living Room mode, and Dynamic become your top choices.
I can say with confidence, that Epson's default Living Room mode is way off, I mean big time! Dynamic you expect to be off a fair amount, as most projectors push color saturation, the color green, and other aspects to cut through ambient light. Both Dynamic and Living room though can be fixed however, or rather significantly improved, reasonably easily.
Bottom Line: The JVC is no fuss at all, out of the box, when it comes to color. The Epson by comparison does very well, but not as good as the JVC in its best mode, but when you go to the brighter ones, something should be done, even if you are not an enthusiast.
Last year the JVC DLA-RS1 set a new standard for black level performance for today's home theater projectors. In fact, until the even better JVC DLA-RS2 hit the streets, I'm not sure there are any home cinema projectors other than the old huge CRT types (CRT's do not have black level issues - they can produce pure black - no color at all), that could do better than the RS1, at any price.
So, here comes the RS1x. Its black level performance should be identical to the RS1 it replaces.
Generally contrast ratios have been a good guide to black level performance, but that changed when some (now most) home theater projectors added dynamic irises to provide superior black level performance on darker scenes.
The JVC RS1x claims 15,000:1 contrast ratio, but the JVC's as a group, do not use dynamic irises, instead they re-engineered their LCoS panels for superior black levels.
By comparison, the Epson Home Cinema 1080 UB (and the Pro version) do have dynamic irises, and claim a record breaking (in terms of non-CRT home projectors) 50,000:1 contrast ratio! (The next closest to that number is the JVC RS2, with 35,000:1.)
Even on very dark scenes with no bright areas, the Epson can't quite match the JVC, although with dynamic irises, there are a lot of variables. Perhaps better would be to say, that at its very best, the Epson rivals the JVC on those dark only scenes. When there are bright areas on the content, though the JVC definitely has the advantage. My point is, though, that the Epson, while not as perfect in this regard, is so close, that I have only tested one other 1080p projector, the Sony VPL-VW60 - which competes directly with the JVC projectors. I'll also give the Sony VW60 the advantage over the Epson, but it is very, very slight, at best.
The black level performance of the Epson is one of the things I love best about it. Not the best, but "close enough" for all but the most discriminating, and close enough for those guys, if the budget doesn't allow for a JVC.
The JVC, produces the more natural or "film-like" image of the two, but the Epson, although slightly "harder" looking is still very good.
Let me put it this way, which I have published previously, in my blog, or on one of the forums: When I recently had in-house, the BenQ W5000, Epson Home Cinema 1080 UB, and Sony VPL-VW40, all at the same time, and could compare them to my JVC RS1, here is my conclusion:
If I had to give up my JVC RS1, I favor the Epson. It is the one, that would keep me happiest. The Epson, although less perfect than the JVC, has strengths that make it more different, than lower quality. By comparison, the other two, were to me, simply not serious competition to the RS1, switching from the RS1 to the BenQ or Sony, left me wanting. Switching to the Epson left me fully satisfied, even though it's not quite as good. I hope that make sense, because that is a key reason I chose th Epson as the winner in its price range. If I couldn't afford the JVC RS1 or RS1x, the Epson would definitely be my lower cost choice!
Neither Epson, nor the JVC RS1, or RS1x support use of an anamorphic lens, so you cannot go pure Cinemascope (2.35:1) with no letter boxes, with either projector. Or, rather, you can, but to do so, you will need to buy an outboard processor, which can cost as little as around $1000, but most are $2000 - $3000+. Epson does not offer any such processors in their lineup, but there are plenty out there to choose from. JVC now offers two different ones, both over $3000.