The more files you have, the more OneDrive tends to chew as a baseline. If you exceed those limits it'll just sit and chew without actually updating anymore. I want to say something like 200K files is the limit.
If you're using it for work to sync build dependencies or your build tree or similar, it's easy to accidentally end up exceeding those limits and watch it eat CPU time totally ineffectually. Ask me how I know!
I run on MacOS and my cpu has spiked twice today already. When I hear the fans, it’s usually OneDrive.
I don’t mind the cpu as I have lots but it might take 30 seconds to sync a new word document before I can share it, so that’s annoying.
With Dropbox it’s almost instantaneous and the file just syncs up.
I’m not sure what OneDrive is doing, but it’s harder to use. I don’t want to slow down and wait for OneDrive to sync before I work with others.