A significant fraction of the time, win10 is indexing files, running antivirus scans, running win update (multiple times a day), etc. This will often pin 1-2 cores. On my dual core i7 laptop from 2016. That’s not good performance. Since I also use ubuntu on a daily basis, I can see the benefits pretty clearly.

I converted a similar laptop from win10 to Ubuntu and now it is all cool and quiet.

Windows seem to require many many CPU cycles just to update itself and index files (yet cortana never seems to find anything, but that's another discussion).