oh I see, I think you mean diffusers with circular (tuboid) holes or polar diffusers.
they offer diffusion pattern that follows a polar 3 dimensional (solid angle) geometry. They are good for places where audience is sitting in a 3dimensional pattern, as in multiple tiers with side VIP balconies.
The skyline offers 2 dimensional diffusion pattern, vertical and horizontal and a basic cavity based QRD diffuser offers diffusion on 1 dimension (horizontal or vertical) based on how it is mounted.
Horizontal diffusion pattern if preferred if there only going to be 1 or 2 people in the studio. Since no one is hanging upside down from a ceiling of studio, vertical diffusion is not super beneficial. Which is why most of the times cheaper 1 dimensional QRD cavity based diffusers are used more.