Un usuario de avsforum que ha tenido el Acer M550, el Viewsonic PX-747 y el Optoma UHD51A, dice que se queda de calle con el 51a.

Cito:
I've had my hands on 3 "4K" projectors. The Acer M550, the Viewsonic PX-747 and the Optoma UHD51A.
I have a dual purpose for the projector and has to be able to handle both adequatelyaytime and Night time viewing with ambient light. Indoor and some outdoor lighting entering the living room. Second but most importantly, it has to be used for a completely darkened home theater in the evening for pure movie watching.
Not used for gaming at all. The clear winner for me out of the 3 is the UHD51A as I've described already in it's dedicated thread. There is a 3 dimensionality that is mesmerizing with the UHD51A that the other two can't even compare to. It is plenty bright.Naysayers might mention that projectors aren't bright enough for proper HDR but the UHD51A is plenty bright which makes images want to leap out of the screen. Another pleasant surprise is also its ability to make an average or below average 4K release look "very alive" that not even my Samsung JS9500 can even do. Not only does it have end to end sharpness uniformity but it actually makes directv images very sharp. Video noise is also very minimal. This is usually a flaw that creeps in with very sharp images but the Optoma's image is very clean.
I haven't had any other 4K Optomas but with my past experience with Dynamic Black, you can usually see it working when engaged. With the UHD51A, it is very discreet and can't even be detected when turned on.
When I do a demo with the 4Ks that I've had, there are a few discs that I test it with to see if it passes the "WOW" test. "LUCY" is one of the demo discs that I use and with the Optoma and maybe because of the color wheel, I am able to see new detail that I wasn't able to see with either the Acer or the Viewsonic. I use a Stewart grey screen and a Panasonic UB900 and feed an HDMI 4K cable directly to the UHD51A for the video.The directv goes through a receiver then to the PJ.