If you want to render your product which has been modeled in Rhino, what render engine would you use?
Vray or KeyShot? Why?
It really depends on your goal: purpose of renderings, speed, ease of use, budget, how often you need renderings, previous experience with rendering etc. Download demo’s/trial versions an give them a spin. Adding to @Lagom’s list: Keyshot, V-ray, Cycles (part of Rhino 6), Octane.
Is there an Arnold plugin for Rhino?
No, but a plug-in is not really necessary.