1) Absolute stability (in my experience).

2) No dependency hell (you do not install what you will never use; one could use pkgsrc, if desired).

3) Does not use the rolling release paradigm (with the need to stay up to date, more or less, in order to avoid breaking the system).

4) More minimalist, saner feel. (It has to be more minimalist, as the maintenance team is small.)

5) No systemd (so far; not that I care much, but still feels nice).

6) Good community support.