I5 Imac VS i7 mac ? Does handbrake work better with Hyper-Threading

i convert alot of 1080p videos, and about to upgrade my mac.

Does hyperthreading have a noticeable speed increase when converting videos using handbrake ?

its quad-core i5 vs quadcore i7 - the only difference being slight speed increase and Hyper-threading

anyone got any numbers to quote (eg. time differences) would be helpful