[CalendarServer-users] 5.3 or 6.0?

I see that both versions 5.3 and 6.0 have been tagged for release. And it appears that work on 5.x continues (there's a 5.4dev branch). I am thinking of upgrading an installation of 5.2, but I am unsure of whether to go with 5.3 or 6.0. Any recommendations? For that matter, are there Release Notes which enumerate the changes from 5.2?