As blacks don't need much help on this projector, I chose a 1.5 gain Video Spectra screen from Dalite. It is electric and can be stopped at any aspect ratio, eliminating the need for masking. It extends to 4:3. I like the punchy picture. Grey screens, for me, and you may feel differently, seem to take away a certain amount of three dimensionality (did I just make up a word?). That and my wife really didn't like any of the grey screens we previewed with different LCD and DLP projectors. I suppose we like our white to be white. When you stop down the contrast to 3000:1 you're getting a really vivid, dynamic and 3D picture.
Well that's my reasoning. I urge you to preview different materiels or go visit some setups in your area and see what suits you and your family.