Compare the other extreme Debian, which is very stable.
In the sense that is unchanging, sure. But that's one hell of a bad word to describe that in this context. In my experience the incompatibilities caused by only ancient versions of things available in the repo of even a newly released Debian are not helpful. Stable wouldn't be the word I choose to describe the situation, or the fiddling and tinkering that results from that. Often having to go outside of the repo to solve, defeating the whole point of said repo.
Arch in my limited experience is much more stable, in the sense of "just works" and always having up to date software. If I want to use something, I can just install it (from the repo), the chance of it not being the current release are slim.