I’ve made some tests with 3ds max and vray with hyper-threading on and off. The results are mixed, it depends on what kind of scene Im rendering.
Render machine: Dual e5-2670v3; 16GB DDR4; Windows Server 2012 R2; 3ds Max 2014; Vray 2.40
Shadow only | 33% faster without HT
Fabric and wood | 14% slower without HT
Glass mat | 35% faster without HT
Why is it slower with HT on when rendering shadows and glass materials?
In some other scenes like the second one, when Im not rendering glass or shadows the difference in render time is smaller or almost identical.