I'm going to nitpick here a bit. More threads does not
always mean more performance (assuming everything else stays constant). Multithreading always comes with a cost, since the efficient distribution of tasks becomes more complicated, and there are cases where you may actually end up losing performance because of this. I know there are many cases where multithreading helps, but even in gaming it's not always the case. Take for example the Total War: Warhammer (DX12) results for R3 1200 and R5 1400 from Techspot's 'Ryzen 3: The Ultimate Gaming Benchmark Guide'. The R5 got (avg/1%) 72 fps / 58 fps and the R3 got 69 fps / 58 fps. Considering that the R3 runs at 100 MHz lower clockspeed, the difference is negligible and there does not seem to be any benefit in having those extra threads.
When Ryzen came out, there were cases where disabling the SMT improved gaming performance, which was then attributed to poor optimization for the new architecture. However, some people claim to have observed benefits in disabling HT on Intel CPUs as well (
http://www.overclock.net/t/1588555/gaming-benchmarks-skylake-core-i7-hyperthreading-test), and I doubt the same optimization card can be played there, since Intel's architecture hasn't gone through any massive changes in recent years (AFAIK). It would actually be interesting if Techspot could do an in-depth article about the effect of SMT/HT in gaming. Comparing the i5-8600K and i7-8700K doesn't quite do the trick, since they have different amounts of cache. And while we already have some idea of the benefits of SMT in 4/4 vs 4/8 -scenarios, this does not mean that the R5 1600 would necessarily benefit from SMT to the same extent. So maybe a i7-8700K "vs" R5 1600, both with multithreading on and disabled, 30 games tested with Vega 64 LC and GTX 1080 Ti... Is that Steve I see running for the hills?