A while back I put together a little experiment to see how hyperthreading affected Houdini. Mainly I was curious to see what the effect was for myself; every place I've worked seemed to have a different opinion, and some sys admins were very adament about HT have no improvement on performance, but rather had a negative affect. I think that info is outdated, as from what I've read HT was like that when it first debuted.
http://blog.cerebero.com/post/157399715043/hyper-threading
Hope its helpful!