JVC DLA-RS20 vs. JVC DLA-RS2, DLA-RS10
Let's start with the RS20 vs. the older RS2 it is replacing. The short version is this: The RS20 is dramatically brighter!
The CMS, etc. will allow slightly better overall color, but a calibration is very tricky, which is why we published CMS settings done by two guys on the forums (one did the bulk of the work the other figured out how to improve on it). Together - between 60 and 80 hours work. (I wonder if they have time to watch movies?)
However, they also tell me, that, while grayscale balance will vary from projector to projector, good CMS will be essentially unchanged from one projector to another. Thus, the CMS settings we published, should be most helpful. Those guys are still not completely satisfied, and I expect they will further revise over the next month or two. (they haven't had their RS20's very long, of course.) If they send me better settings, I'll update the review, and or put up a blog about it.
JVC has stayed with Silicon Optix Reon processing (the RS20 probably has a slightly newer version), but there were no significant issues with the older processing in the RS1 and RS2) at least I've never had a complaint with 1500 hours on my RS1.
That pretty much covers it. If you want an anamorphic solution, I'm waiting to hear back if JVC's is ready. The one they offered for the RS2 can't get close enough (with that setup's lens sled) to work with the RS20, which has the lens further recessed.
Black levels may be a hair better on the RS20, but without an RS2 for a side by side, hard to say. Any improvement is going to be slight - far less, than say between the RS2 and RS1, or RS20 and RS10. "Incremental improvement" probably would describe it.
So, ultimately, the RS20 should, with an optimum calibration, do a bit better in terms of color accuracy, skin tones, etc., than the RS2, but it really comes down to brightness. If you have a smaller screen, for example, a 100", then you can stop down the iris quite a bit, with the RS20, providing another incremental improvement in black levels.
That brings us to the RS20 vs. the RS10. I'll cover the basics right now, though I'm still working on the RS10 review.
Brightness is very close, in "best" mode (Cinema 2 on the RS20, Cinema 1 on the RS10), the difference is just a few percent. In brightest mode, the RS20 ended up slightly brighter, but, let's just say both projectors are pretty much equal in brightness.
There is still a notable difference in black levels favoring the RS20. On many mixed scenes, mostly dark, but with some bright areas, it's hard to tell the two apart, but on scenes that are pretty dark overall, the RS20 shows off its superior black level abilities. Between the two projectors (post calibration), I give a slight edge to the RS10 in showing off dark shadow detail. This isn't surprising, as the nearest thing to black is darker on a projector with better blacks, and therefore harder for the eye to discern. Call it a non-issue, adjusting Brightness by one number in either direction and one projector can go from being the better, to being the worse of the two in shadow detail.
While the RS20 is a tricky calibration, the RS10 without the CMS is much simpler, and I should point out, produces better results if you just do grayscale calibrations on both (no CMS with the RS20), you'll like the RS10's skin tones better, etc.