Install ,Upgrade and Patch Vs Fresh and Clean installation

"Doing a fresh install usually gives you the best performance. However, it also means wasting a lot of time reconfiguring everything and making them work like before.

Upgrade and patch is the easiest way to do it, but I've sometimes had a lot of problems with this approach (especially with Firefox). The big advantage is that all the settings are kept intact (if the patcher or installer is worth anything). I've recently upgraded a Windows Vista install to Windows 7 and everything worked extremely well; all the software was in place, all the drivers were working. If I'd have to do it again, I'd go the same route."

Depends, do you have an example? This should also be a community wiki if the original question is clarified.