Difference between the red dot and holographic sight?
Solution 1:
There is no statistical improvement by any of the scopes, they just give you further zeroing distance and allow you to shoot enemies at a further range with (relative) ease.
The only differences between RDS and HS is as you mentioned, the size and shape of the physical sight as well as the reticle, and according to this source, the holographic zooms ever so slightly farther.