Chamber dimensions and headspace are the only factors in case support. Whether the barrel has a feed ramp or not doesn't matter.
Well, most ramped barrels offer greater case support over a non-ramped barrel. This is because the chamber goes back a tad further. If you were to take the same reamer and cut a chamber the same depth, the ramped barrel would offer a touch more case support.
I have non ramped barrels in my 1911's that support the case back to the web of the case. I agree with JOG they support the same unless someone did a poor job on the tapering the bottom of the barrel which happens
The deciding factor is the angle at which the ramp is cut. Ramped 1911 barrels have a steeper angle on the ramp than a Glock, so they intrude less into the chamber area.
So when you really get down to it, it is the angle of the ramp, and how far it intrudes into the chamber. Vary that angle on identical chambers and you have varying degrees of case head support.
