The official Sync is focused on providing a more integrated experience in the Obsidian app

- Built-in version history

- Cross-platform support, especially on mobile

- Fine-grained control (e.g. different theme/plugins/settings per device)

- Sharing your vaults with other users

I've been using Synology Drive to sync Obsidian between different machines and my android phone and it works great. I've never seen a need to use the official sync.

Synology Drive is a file and folder syncing system.

Obsidian is a note and wiki syncing system.

You should use an obsidian syncing system if you want to sync notes and wikis. You should use a file syncing system if you want to sync files.