Official comment
If you don't want to lose your database / settings, I don't recommend uninstalling everything, simply install a new version over the old one and it will replace the necessary system files.
For Windows, you don't want to install 6.0.1 right now as there's a problem, you can install the 6.0.0 version, or the 6.0.1 beta instead (which doesn't have the issue).
If you want to FULLY uninstall EVERYTHING, you need to remove these folders after running the uninstaller:
Win 7/8/10:
C:\Users\yourusername\AppData\Roaming\Pioneer\
OSX:
/Users/yourusername/Library/Pioneer/
/Users/yourusername/Library/Application Support/Pioneer/