back when I used debian(10 years ago) testing was the staging ground for the future stable version, so it got a couple of issues that varied as the mantainers s

back when I used debian(10 years ago) testing was the staging ground for the future stable version, so it got a couple of issues that varied as the mantainers stabilized the system. then unstable was a really rolling release system, in my experience more stable than testing(understandable quirk as is was used by mantainers to prepare the next release). At that point I decided that I'd rather use arch then unstable debian, but unstable was quite similar regarding package candence and stability.