Depends on which category you fit into. You use dev tools and stuff like homebrew/macports a lot: fresh install is a lot nicer. You don't use the above that m

Depends on which category you fit into. You use dev tools and stuff like homebrew/macports a lot: fresh install is a lot nicer. You don't use the above that much: Upgrade is fine. As for the packages, I had a lot of different packages that were built for Mavericks, and needed updating, and would constantly bump into something new that needed something reinstalled etc. Various reasons for this, like Apple moving around system utilities and upgrading various things. EDIT: Just to be clear, all is solvable with the upgrade. It's just a bit cleaner with a, well, clean install ;)