Hi, thanks for the detailed tests. I've repeated them here:
i7 980x 3.8 Ghz
RailClone Pro 2.5.0
Test01. Using RC:
Test02. Collapsed to mesh:
As you can see there is difference, but not so much as in your case. Unfortunately we have not a similar computer with Windows 10, so i cannot test that configuration.
Instead, i tried using the latest V-Ray nightly build (3.25.01) with a custom RC compiled with that version. There is a significative improvement:
Test03: Using RC:
Test03: Collapsed to Mesh:
RailClone rendering is even a bit faster that using a pure mesh.
Sincerely, i have not idea what may be causing that problem in your workstation. It may be due to RailClone, V-Ray, Max 2016, Windows 10 or a combination of all (most probably).
But in this case i suggest we wait that V-Ray 3.25 is released (we'll publish the RC update short time after) and try again. Hopefully the situation may change to better.
If you have access to the V-Ray nightly builds and want to try it, i can send you the RC update.