Hyperthreading is significantly more efficient switching between threads on the hardware level (as opposed to the software/OS level) and you get more full utilization out of the hardware. But it isn't as good as another actual core. So while hyperthreading is about 40% more efficient per core for running multiple threads, whereas another core is 100% more.

That is of course only if you're putting them to use. Most games now are pretty good at using 4 cores, because those have been around a long time, but very few games gain much for more cores. So having extra cores is nice but it isn't going to have much of a difference on most games. There are some things that do benefit from it, a few games too, but not a lot. Chances are if you're actually doing something that will make use of 8-16 cores you already know it.