On relatively bright scenes, the BenQ looks very good post calibration, and not as different from the Epson as it does with scenes with a lot of dark areas heavy in color.
The Epson 8500UB just looks more "regular" the colors don't quite jump out at you the same way, but the Epson image is also a very dynamic one, that I describe as having a lot of pop and wow.
So, both have a good, dynamic look, but due to the different color handling, they still look rather different. Which is better? In this case, the one that works best for you, in your room. Buy the one you like, if its image pleases you more. Other than black level performance, these projectors are, in terms of picture quality, more different than better/worse.
The W6000 projector got a good boost in brightness compared to the older W5000. The Epson is simply no match for it when comparing best modes, with the Epson topping out at about 500 best mode lumens compared to the BenQs 866 lumens with Brilliant Color off. While many implementations of Brilliant Color tend to be a little too "over the top" to be even considered as a "best" mode, the W6000s Brilliant Color on implementation (measured 1039 lumens) is particularly good.
For those wanting the most natural film-like look, you'll still want Brilliant Color off, but many people will be perfectly content with Brilliant Color on, in terms of overall picture quality. That the W6000 with BC on, looks a lot more natural than my new Samsung 40" (120hz) LCDTV, in Standard mode (nevermind Vivid mode), says a lot. You'd have to drop the Samsung down to it's Cinema mode to look as natural as the BenQ even with BC on... Go figure. In other words, the typical watcher will favor BC on, for the extra almost 20% more lumens.
OK, so, if you want to use best mode, the BenQ easily crushes the Epson.
When you do want some lights on intentionally, or can't fully darken your room, then the BenQ again has a big advantage in lumens, 1750 to 1309, even though the Epson is the 3rd brightest in the class, and much brighter than most of the others. The thing is, the BenQ in brightest, is really, really heavy on green, and you can't really adjust color in that mode.