These all new, pixel shifting, 4K capable "Ultra Black" projectors from Epson; the Home Cinema 5040UB - aka HC5040UB - and Pro Cinema 6040UB - aka PC6040UB, are far more advanced than their predecessors, in almost every way.
The improvements over the past four or five years in the UB line have been modest. Not this time! There are so many new goodies that Epson even substantially raised their price. Despite that, I consider these new models to easily be the greater value compared with last year's.
The Home Cinema 5040UB - $2999, and Pro Cinema 6040UB - $3999, are virtually identical except for price, the case color, and that the "Pro" version comes with a cable cover, a spare lamp, plus an extra year of warranty and replacement program, for the higher price point. They are sold through different distribution channels with the HC5040UB available online and locally. The PC6040UB will be found at Epson authorized local installing dealers, and installing big box houses. (A Magnolia Home Theater store in Best Buy would count as the later.)
Update April 2017: Epson just lowered the price of the Home Cinema 5040UB to $2699 - a 10% drop, making the most popular projector capable of working with 4K and HDR even more affordable.
Simply stated: The HC5040UB is the more accessible projector of the two, but the PC6040UB is the one you will more often find at a dealer that can install it for you - and a screen, and a sound system, and even motorized shades and home theater furniture if you need them. There is one more model in the series, that's the HC5040UBe. It is $300 more than the standard 5040UB. For that you get wireless HDMI with 4 wireless inputs and support for MHL.
One more thing - up front - for you gamers. The HC5040UB and PC6040UB are much better at input lag than their predecessors. (You'll find more about it on our Special features 2 page.)