I use this after having used Google Authenticator, what made me switch is easy backups and restores, not to the cloud but locally to a file. Also you don't need a Google Account if you wish to transfer your data to a new device.

I can’t tell from the homepage, but perhaps it supports SHA256? Google Authenticator on Android (but not, weirdly, on iOS) pretends to be fine with SHA256 but then goes ahead and uses SHA1, and thus generates wrong codes.

Being open-source is not of exclusive benefit to non-users.

Additionally, being non-Google would be considered a large benefit by many non-technical users I know.

Better UI and custom icon support for the random website you have.

Plus this is offline. Hence more secure.

You can require biometric authentication to view the codes, that's the main reason I use it over GA.