Perhaps the most significant differences are this: The Sony isn't as versatile, in that it isn't anywhere near as bright as the Epson when you need maximum lumens for viewing with some ambient light - typically HDTV/TV/Sports. The two are similar enough in brightness in their best modes, but when it comes to watching the "game", the Epson has a clear advantage.
Also, when I trick out the Sony and come up with about 900 lumens, its color balance is no match for the Epson, when it is outputting over 1500 lumens. Even the Epson in its unadjusted Dynamic mode, produces a better color balance, and in that case, the Epson has over 1800 lumens - twice that of the Sony. Then, there's Epson's two year warranty, with overnight replacement for both years, compared to Sony's basic one year warranty.
Sony VPL-VW40 vs. the DLP projectors
The Sony simply produces blacker blacks than any of the DLP's recently tested. And, it is a significant improvement. DLP projectors have their own flavor, and some would say, they have more depth than the LCoS or 3LCD competiton, but, again, each technology has its advantages.
From a brightness standpoint, most of the DLPs match or slightly beat the Sony in best mode, and the same is true for brightest modes. The Optomas (notably the HD8000/HD80 in particular), typically will output around 1000 - 1200 lumens in brightest modes, and deliver slightly better color than the Sony, doing the same thing. However, from more of a purist standpoint, the real advantage in black levels of the Sony, make it superior to any of the recently tested DLP's, in that regard.
The possible exception are the incredibly bright, and very expensive Optoma HD81-LV, and the really expensive Sharp Z20000, both of which are more than double the price, and not really direct competition.
Sony VPL-VW40 vs. VW60 projectors
Well, the VW60 does better black levels, costs more, but comes with a 2 year warranty. If Sony is your thing, buy the VW60 if you have the extra bucks, but then, you need to also look at the VW60's closest competition, for even more money.
Sony VPL-VW40 vs. Panasonic PT-AE2000U
Both are film like, but there is a big difference in black levels, so while I really like the Panasonic PT-AE2000U, and many of its features, I definitely lean toward the Sony.