Optoma GT720 - Projector Screens

Unless you have a serious ambient light problem, let the GT720's brightness do the work for you. I'd skip thoughts of a high contrast gray screen, unless you have a real, specific need. That many games can be dark, going to one of those HC gray screens isn't going to make those very dark areas any easier to see.

Stick to nice 1.0 gain or higher white surface screens, unless you are buying this projector first, for movies, and only 2nd for games. If that's the case, there's probably, a better Optoma for your usage than the GT720.

If you plan to be 3D gaming with your GT720, same advice - use a white screen. The GT720 uses a standard screen, it does not need a 3D optimized screen - those are normally reserved for systems using passive 3D glasses. If you'd like some guidance regarding screens and 3D, check out RonJ's blog, that's a topic he's covering in his initial 3D related blogs.