These projectors are in two completely different price ranges (and different categories in this comparsion report). The Home version of the Epson is selling for upward of $2500, and the Pro version for about $1000 more. (The Pro comes with a ceiling mount, and also a spare lamp, which together could be valued around $500. Also the Pro Cinema 1080 UB, comes with a third year warranty, for that difference).
By comparison, the JVC DLA-RS1 typcially sells for around $5000, or now, I would assume (don't know) less, now that it is being replaced by the DLA-RS1x, which should stay closer to $5000 for the immediate future.
So, that means that the Epson can be not much more than half the price, if you go with the Home version. That makes the Epson my choice if you can't afford a JVC. Whether to buy the JVC, if you can afford one, compared to the Epson, will depend on how much you are willing to spend for a slightly better, slightly more natural, overall picture quality. When comparing these two, it's about diminishing returns.
Art's Two Cents
I think you've figured it out. If you want a great projector in your home, but are limited on the bucks, one of the Epsons is the way to go. If you are seeking that last extra bit of exceptional performance, and budget allows, spring for the JVC.
That's my general guideline. Another reason, for spending more on the JVC projectors, is that the JVC's are definitely brighter than the Epsons when both are in "best" picture quality mode, so for larger screens, the JVC definitely has a significant advantage for movie watching.
Of course, there's always a catch. If you are also a big TV / Sports fan, and can live with less than "best" mode performance for that type of viewing, the Epson is almost twice as bright as the JVC. With a "tuned" Dynamic mode on the Epson putting out over 1500 lumens, while the JVC measured just less than 900 in its best mode. I think that extra horsepower on the Epson's in brighter modes is another key reason why the Epson is an exceptional value.