Thank you for the informative and neutral response. I knew there was a larger debate over the two, but I didn't have a good enough understanding of the two to know why.
barrkel talked about systemd as a replacement for init, but that's not the goal of its authors. Nor was there a debate over the two.
There was a debate in Debian Land over at least four choices: systemd, upstart, OpenRC, and sticking with van Smoorenburg rc with Debian's various enhancements.
The stated goal of the systemd authors pretty much from the start was not to "replace init", or even to replace both init and rc. What barrkel wrote could be said of daemontools from 1997, after all. That, too, encouraged a move of common procedures and mechanisms out of bespoke daemon programs and scripts and into a common daemon management system.
systemd, rather, was to provide a common layer, beneath everything else and above the kernel, used on all Linux operating systems. Its authors saw the differences such as /etc/sysconfig/network versus /etc/HOSTNAME versus /etc/hostname versus /etc/conf.d/hostname and wanted to unify all that, so that all Linux distributions worked the same. They didn't just write process #1 program. They wrote a name-lookup server with a local protocol to replace the DNS protocol (and the protocol that GNU libc uses to talk to its lookup helper processes), a network interface setup/teardown utility, a whole bunch of service utility programs such as a program to save/restore randomness from /dev/urandom across system restart, a centralized log writer, a centralized login session manager, and a whole bunch of programs that provided RPC interfaces, over a centralized system-wide Desktop Bus instance to GUI tools running on user/administrator GUI desktops, for things like setting the default timezone and pretty-print hostname. To that they added rules about where to find different sorts of stuff, from administrator-written unit files to /etc/machine-id; guarantees about "API filesystems"; rules about /run, /run/user, and a whole bunch of related memory filesystems; deprecation of things like /var/run/lock; rules about what sockets old syslog programs had to change to using, in place of what they had been; per-user service manager instances and a whole extra set of PAM hooks that connected it with the new runtime directories and the login session manager; and requirements such as that /usr be already available at the point that /sbin/init is invoked from the initramfs. They got some additions made to Linux in support of this, such as subreapers; and failed to get others, such as kdbus.
"systemd replaces init" is both superficial and a blinkered Debian world-view. In the world outwith Debian, in Ubuntu Land and Fedora Land, systemd replaced upstart, which had been the Fedora and Ubuntu system and service manager for a number of years before systemd was invented. The world has never been van Smoorenburg rc scripts versus systemd, not even when the whole Debian debate was had.
* http://jdebp.eu./FGA/debian-systemd-packaging-hoo-hah.html