iCloud Drive gets confused every time I have to logout of iCloud and log back in on either my iMac or my MacBook because it stopped synchronizing Safari tabs, and then tends to present me with several versions of my files and claims to have identified hundreds of conflicts.

Personally, I use Dropbox (free) for my important stuff and iCloud Drive (200 GB $2,99/month plan) for everything else on my Macs because Dropbox is much more reliable than any other Cloud service I have ever encountered. It was a bit of a mess to setup but once we've had it up and running it's been quietly doing its job. I know my dad uses it to exchange files between his Android smartphone and his Mac Mini as well as making regular backups of his most important documents, and I haven't heard any complaints for a very long time. I've tried Google Drive once on Chrome OS and Windows, and it worked pretty well in the short time we've had together. My wife uses it on her iPhone to backup photos and sync them with her Windows laptop, and she's seems quite happy. I've been avoiding it ever since though, and I've never used it on macOS so I can't comment on that. In all fairness I should add though that this was in early 2015. I've had OneDrive running on Windows 7 and 10 for quite a while but no longer do because it went full retard on me several times, and frankly I simply got sick of it.

Onedrive vs google drive vs icloud