macOS 27 is way faster and more stable than macOS 26 though, so unless you are on an ancient version it doesn't make sense to not upgrade.
macOS 15 still gets security updates.
I've hit some really weird window/workspace UI bugs so far in MacOS27. It's not no-brainer update yet, IMO.
On one of my machines, I don’t know if I could even make it fit. So it’s a no-brainer to not update on that one, if they are going to force an extra 14GB download on me.