The 85B is only different than the 75B in that it has an ambi-safety and slide release. These are musts if you're left-handed and simply nice if you'd like to practice with either hand.
The 85 Combat is a different animal. It still has the ambi controls, but it also has a variety of finishes available, an adjustable rear sight, an adjustable trigger, and no firing pin block that some people think messes up the trigger pull somewhat on the B models. Oh yeah, the 85 Combat also allows the mags to drop free American style as it ditches the magazine retention spring found on "lesser" CZs, though both 75 and 85Bs can be easily end user modified to "relax" the spring. The mags are interchangeable and I don't know why the mag release isn't reversible when all of the other controls can be ambi.