How to save/restore Sublime Text 2 configs/plugins to migrate to another computer? states that, to backup a Sublime Text 2 installation, a user should preserve the ~/Packages/User directory (from the user’s local data folder on whatever OS they’re using).
However, http://andrew.hedges.name/blog/2012/01/19/sublime-text-2-more-sublime-with-a-drop-of-dropbox and most other walkthroughs for using Dropbox to sync Sublime’s settings specify three directories: ~/Packages, ~/Installed Packages and ~/Pristine Packages.
What is the functional difference between backing up just ~/Packages/User, and the other 3 directories?
I think that Packages/User is the one in which you are supposed to put settings (according to Sublime’s official and unofficial documentation). However, some people put them in the other folders from time to time.
The Dropbox advice may be a hedge against poor practice.