Curved screens do have some distinct advantages, especially in installations where the throw is very short (1.6 or less) and pincushion distortion becomes an issue. Note that most curved screens are actually “cylindrical” in that there is no curve up and down – only from left to right. Advantages of a curved screen:
Curved screens help compensate the pincushion distortion that occurs when an expansion-based anamorphic lens is used because an inward-curving screen naturally produces a form of “barrel” distortion which can partially compensate for the “pincushion” from the lens. As you can imagine it can be complicated to determine how much curvature you need in the screen to compensate for how much distortion is in your short throw-ratio installation. But even in a general sense, the higher the throw ratio, the less noticeable the distortion, and therefore the less of a “need” for a curved screen.
For some people a curved screen can bring you an even greater sense of immersion when watching movies. The slight curvature of the screen gives the impression of the image wrapping around you, involving you in the action to an even greater degree. The opposite view is that a flat screen is more like a window into the movie. Either viewpoint is valid and “best” is up to you.
Curved screens can deliver a more uniformly illuminated image for centrally localized seating with less “hot-spotting” since light that would normally be reflected to the side is instead more effectively directed back to the seating area.