The grey screens (or darker) are mostly used to darken blacks slightly for projectors with poor black levels and to deflect ambient light from near-screen sources to assist in poor rooms. In a decently darkened room using a projector with respectable black levels the grey screens don't have anything to really improve, so they mostly just bring negative aspects such as color problems, sparkle artifacts, narrower viewing angles, more noticeable grain/texture, or higher than average price. They all suffer at least some small degree of most of these problems..even if it is very little. While a smooth white screen will suffer none, and work just as well or better in a decent room with a solid projector.
Both the JVC and the Sony are great projectors that deserve a fairly darkened room to appreciate.
The other problem is that the darker/reflective screens can only fight light from closer/sharp angles, so overhead cans or lamps near the seating (where it makes the most sense to help you see) will still hurt the grey screen's contrast and black level just as badly as they would a white screen.
Last edited by Ftoast; 06-24-2014 at 04:48 PM.