Well that mobile dual-core is not really more powerful than your 8 cores desktop, but single-thread performace sure is a weakness of the AMD FX, so user interface etc. may actually be more responsive on that laptop.
And I just realize that FPU pipelines only matter if you work with float color spaces, while the above benches test 8bit int/channel only from what I can tell…now I’m even more curious how Ryzen 3xxx compares to Ryzen 2xxx 
<another edit> hm composite ops for 8bit integer still seems to do a bunch of float math though, I really should dive into that topic some more eventually…
But maybe that’s good to mention anyway, AFAIK (@dkazakov correct me if I’m wrong), so far Krita is only hand optimized for good old 8-bit integer channels and for 32-bit float (HDR image editing).
16-bit integer could be more optimized, while 16-bit float is not supported by CPUs natively, so it gets converted to 32-bit float first, only the conversion itself could be optimized some more.