When it comes to sharpness, I'll give the Epson's a slight advantage, as well. The de-focusing issue of the Epson's weighs in here as well. If your Epson is focused after it is warmed up, it can create a touch better sharpness. Pixel alignment will be a factor as well, when it comes to sharpness, so that a JVC with excellent pixel alignment, may well appear a bit sharper than an Epson whose pixel alignment is off a little more. Either way, the Epsons and the JVC's are in the same general place in sharpness. Neither brands are quite as sharp as the sharpest of the 1080p projectors, such as the InFocus IN83, and typically, several other DLP projectors.
Being more "film-like" is an advantage of the RS20. This is to a degree about personal taste, rather than a definitive advantage. Epson offers a lot of pop and wow to their image, which also makes it a touch less film-like. The RS20's THX mode, for example, I found to be a bit flat (lacking the more dynamic look of the Epson projector).
If you are interested in going with an anamorphic solution, that takes the 6500UB out of the equation, since it lacks internal support for an anamorphic lens. Sure, you can solve that with an outboard processor, but it would be less expensive to just buy the 7500UB (which has the support).
The Epsons offer a touch more placement flexibility, but the very small difference probably wouldn't impact the decision of more than a couple of percent of the people considering these choices.
The RS20 has motorized focus, zoom, and lens shift. That's always nice to have - consider, it's a bitch to get a perfect focus with the Epson projectors when you are 15-20 feet back from the screen when focusing the projector. With the JVC, using its remote control, you can do the focus with your eyes no more than one foot from the screen.
The Epson's have taken some "hits" in reviews (like mine) and on the forums for some significant issues with their frame interpolation methods, but then JVC, like most manufacturers, don't do any creative frame interpolation. Actually as it turns out, the serious Epson issues tend to relate to creative frame interpolation of 24fps movies, to 120hz, creating 4 new frames between each two original frames. The only other projectors pushing creative frame interpolation (the Sanyo PLV-Z3000 and Panasonic PT-AE3000), don't even make the attempt. Neither adds more than one creative frame, and only from 60fps sources, not Blu-ray movies at 24fps.
So, if you like creative frame interpolation for sports, the Epson has it for you, and does it fairly well. For movie watching, using 4:4 the Epson offers 96fps compared to the 48fps of the JVC RS20.
Brightness is a trade-off, depending on your own viewing requirements. The JVC is substantially brighter than the Epson in best mode, while the Epson projectors are roughly twice as bright as the JVC RS10 when comparing brightest mode. In terms of screen size, whereas the limited brightness of the Epson projectors' best mode, limits you to screens of 110" diagonal or less, with most normal screens (gain of 1.4 or less). On the other hand, the JVC can handle my 128" diagonal screen, with lumens to spare for movie viewing. The JVC has enough for sports and HDTV viewing filling my whole screen, with goog lighting control, without fully darkening the room. By comparison the Epson, in brightest mode handles my room and screen rather effortlessly, compared to the JVC.