When you're buying a Synology you're not just buying hardware but also a pretty dang solid software suite. I've used several NAS products along with FreeNAS, Windows File Services, and plain old Samba. Synology has always been just about the easiest to use with excellent mobile and web apps for accessing your files on the go. It all depends on what you're really wanting out of your NAS.
in my experience it's really really really worth it, though.