Debian didn't decide. Or rather, they discovered that any attempt to force a decision would fail, so they decided not to decide.
In any case, I am fairly optimistic that post-Wheezy the "best practice" way to start a service in Debian will be a native systemd script, with auto-generated SysV-ish shell scripts and/or upstart-esque config files, whenever there are no special requirements.
How much time will elapse until then, I have no idea and refuse to speculate about. This is Debian, after all. :-/