Typically, one of the biggest limitations of screens is the ceiling height and viewing angles for multiple rows. If using a 16:9 screen you simply cannot go as big in many rooms as you run out of vertical space. For example let's say you screen is 6 feet tall it would be 128" wide. For a 2.35 screen it would be the same height but would 169" wide. That's over 3 feet more screen. A 2.0 picture if you use lens memory preset would be 144" wide, so the black bars on the sides of the picture would be not as big as when watching 16:9 material.

I think the ideal solution is an anamorphic lens. You can easily stretch 2.0 material to 2.4 without making people look too wide. But without an anamorphic lens there is no downside to going 2.35/2.4 screen. You still get the largest 16:9 picture you can get for that room. If the room is much taller than wide then you could go with a bigger 16:9 screen. For most rooms, I don't see a disadvantage of doing 2.35 except that you have black bars on the side when watching 16:9 material.