For desktop I run debian sid (unstable), despite the name it very rarely breaks. And once in a blue moon when it does it gets fixed in a few hours/a day. Usually it is just some package that doesn’t play nicely with something else, so not like it is unusable during that time.
The unstable part is that they do not guarantee that it will work, it is still more stable than most other distros and you get new packages.
Testing doesn’t get security updates as quickly as unstable, or even stable sometimes.