I think it's fair to say that this fork is far more significant.
I think this fork will be fairly insignificant, and, further, that it will increasingly run into problems as desktops and other packages depend more and more on systemd components (that trend was one of the major factors in the Debian decision to adopt it).
I actually wish the Devuan guys all the best; I'd love to see another solid server-focused distro (server focus may help them avoid the issues with DEs). But I'm really glad to hear about this fork because the systemd debate has been a huge distraction to Debian. Hopefully this will finally put it to bed as all of the systemd opponents leave Debian for Devuan. I think that will be a net win for Debian because most of the vocal opponents don't contribute much code anyway.
Personally, the more I learn about systemd, the more I like the ideas behind it, and both code and documentation seem to be of high quality (documentation in particular is much better than is typical of open source projects). I'll be sticking with Debian.