Isn't the main disadvantage the one where there's a single drive, so, a single point of failure? So, no multi-drive RAID/ZFS support. This seems like a huge dealbreaker for anyone that cares about backing up their data locally.
The Synology BeeStation positions itself as a beginner-friendly backup solution. While it doesn't have all the bells and whistles of a full-fledged NAS, it is a reliable solution that lets you back up and access your data from anywhere.