Just to add a recent test on the subject as of 2018 and Cubase 9.5 Pro; I just ran a few project loads and exports both with and without HT, using an i7-6700K @4.6GHz machine.
There is no difference in any load/performance times, and export times are the same within tenths of seconds, ie.no discernible difference whatsoever in any use that I could notice. Used rather a heavy project that took 2.32 minutes to load and 2.27 minutes to export, and a much smaller one that did both in well under a minute.
The temps and fan speeds were unaffected as well.
The only interesting difference was that looking at performance graphs, with all 8 logical cores on, CPU usage was reported at around 50% all the time, with just one core going at about 100% and the rest 7 just around 20% or so.
However with just 4 cores, all cores reported about 100% usage as well as overall it was around 100% constantly.
Nevertheless this had no effect on actual performance speed, temperatures, or anything that I could see.