2.35:1 screen = 21:9 ratio. Most of US and European movies are in 2.35:1. So, no black bars over and under the video image if these types of movies are projected to 2.35:1 screen. Projectors in native 2.35:1 should be very expensive and you have limited choices. Viewing 16:9 content will have left and right black bars.
With 16:9 screen, you can use 100% pixels of most home use projectors (i.e. 1920 x 1080) and 100% screen size in watching HK TV digital channels and most of HK concerts BD. But black bars exist when playing movies in 2.35:1 aspect ratio.
I did compare different material of OS screen, and finally choose BU201, cos BU201 has higher gain and is good for 3D, for 2D it might be a little bit too bright, but you can choose economy mode (something like that) from the menu of AE-7000!