I have all my passwords in OS X Keychain too (why would you use an external password manager when your OS comes with a perfectly good one). I did not switch from Safari to Firefox until I discovered above addon many years ago, and I won't upgrade to 57 until Mozilla either fixes the SDK so the addon can be ported or (better) integrates into OS X Keychain like a well behaved Mac application should.
I assume this is in reference to using the builtin macOS keychain? It syncs just fine to iOS as well if you use iCloud Keychain. That's obviously not possible with Android, but you don't necessarily need a 3rd party password manager if you're only using Apple products.
