Debian unstable is not really unstable, but it’s also not as stable as Ubuntu. I’m told that when bugs appear they are fixed fast.
I ran Debian testing for years. That is a rolling release where package updates are a few weeks behind unstable. The delay gives unstable users time to hit bugs before they get into testing.
When I wanted certain packages to be really up-to-date I would pin those select packages to unstable or to experimental. But I never tried running full unstable myself so I didn’t get the experience to know whether that would be less trouble overall.