I've used both, and prefer iCloud. I find it more transparent than OneDrive. OneDrive is kind of like Dropbox, in that it feels like an add-on to the system, not an integral part of the system like iCloud does. It's yet another thing that Apple has done better than Microsoft.

I do wish there was a Windows version of the keychain, though. I work on both Apple and Windows machines, and have to maintain a password manager that works on both platforms as well as the Apple keychain, since it is easier to use on Apple devices than my cross-platform choice.