can it be that bump maps are slower then displacement?
i have a material with blurry reflections on a object where i use displacement and because i thought maybe bump mapping will be faster i removed the displacement and used the displacement image as bump map.
now it looks like (the image is not finished yet so i can ntot say for sure), that bumps render slower.
i thought that displacement should be slower, not?
Displacement should be slower if you render with GI because then the solution will be more complicated where the displaced parts are. Without GI and only regarding to reflections, I don’t think displacement will be slower to render than bumps.
I have not done extensive testing but I have noticed that displacement is often faster than bump maps. My guess is that V-Ray prefers the actual geometry over calculating how the bump map would effect the bounces. It would be great if Vlado would give us some clarification on this. 
Yeah that’s possible that it’s just easier for reflection calculations to have real geometry. Sounds logical!