I made a gradient from 0-1 gloss with 5% difference between each column. The idea was to use it in Glossiness, black diffuse, 100 ior, white dome and compare the reflection pass between V-ray and Corona.
Everything went according to plan, but then I got some weird results with Corona, so I can't compare them. I have no idea if these graphs/curves are useful, but I thought I could share them in case they are.
You can see that pure black is around 0.15y V-ray GGX and 0.24y V-ray Blinn. 0.24y Blinn is the same as around 0.29x GGX on the graph. We can look at the original gradient and find the column that is 0.29x on the graph. This is the glossiness value of GGX that is 0 Blinn. If only the Corona test worked.
This is the glossiness texture I made
V-Ray GGX with default 2.0 tail
V-Ray Blinn
V-Ray Ward
V-Ray Phong
This is the weird result I got with Corona. At first I thought it was pure white.
But then I applied a Gamma Correction and got this result.
Looks like the walking pattern of a drunk.