Within a release train, 2.7.x, we always intend for each version to include fixes for encountered issues. They are all stable. The most recent one includes the most fixes.
Rarely, a release may contain a fix that inadvertently breaks something else. That is rare, but it can happen.
The best way to think about it is…
It’s Couchbase’s responsibility to let you know of anything fixed, known issues and changes in the release notes for a given release. The user deploying an app knows what features it uses, what topologies it’s deployed into, what kind of configuration it uses so they know best if they should pick up a given update.
A user need not always be running “the latest”, but if they never update then their probability of hitting a known issue goes up quite a bit.
Most stable is generally the latest within a given major-dot-minor release train and as long as it’s supported, it doesn’t matter which version of the server. Still, check the release notes for anything specific.
Hope that helps!