whats more important for audio ?
ime huge single thread performance is great..
is reaper still the only proper multi threader ?

 

Cubase, Pro Tools, Studio one, even FL Studio have real good multi-thread optimizations, and to answer your question, quite a bit of both, as what really does matter is the CPU real time processing power, and that might differ, what i suggest for now, is buying a a 3rd gen Ryzen cpu with a good real Mobo (Or even an Intel one, as i own an Intel system), and real good ram KIT, as that's where the magic actually is, a bit of targeted OC, and ram timing tightening will yield way better performance boost.

i've gone trough the trouble doing what i suggested, i can now have a mix with heavy plugins plus a limiter on buffer of 32 and still able to play through it without glitches, as the project continue to grow making it 128 was good enough to have a fully mixed song played without any hiccups with more than 20% of Real-Time-Processing-Power left over.

 

Informative video:

 

the ultimate advertising video for lite OS and mobo with less pci e devices as possible

 

This morning, out of curiosity, I did a comparison between Pro tools 12.5 & Reaper 6 with hyper-threading off vs on.
A Xeon E5-1620 V2 performed like a i5 with Hyper-Threading off. Could not load more than 16 tracks with 4 plugins each (Acon digital Mastering Suite less dithering). Had to increase buffer to 2048 to get steady playback.

With Hyper-Threading on, 32 tracks & a buffer of 64 saturated Pro tools between 90 to 100%.
With Hyper-Threading on, 32 tracks & a buffer of 64 saturated Reaper between 75 to 90%.