Based on what evidence? I don't do a clean install every time a new service pack comes out, or for that matter when a normal windows upgrade comes out.
Haha, based on what evidence?
Try to think of it this way. Do you swim? I happen to be a swimmer. I swim like a fish, actually. One thing I've always noticed with beginner swimmers is they always try to swim with their fingers completely spread. My advice to them is always "don't spread your fingers!". Now, imagine someone coming along and asking "what evidence do you have that swimming with fingers together is better than swimming with fingers all spread out?"
I would only stare at them, blink once, and then ask "I did not just hear that did I?"
No, I don't have any scientific study to reference. But anyone who knows how to swim will tell you that it's common sense to close the gaps between the fingers. They don't build paddles with holes. And people don't use nets to paddle their canoes.
Upgrades are more convenient, yes. But based on my years of working in IT as well as the collective advice of all IT departments out there, it is always better to do a clean install than an upgrade.
When programmers put together an upgrade for an OS, they couldn't account for everything that the individual user has done to his device. Data from the old OS might not work well with the new OS. Left-over cache files might wreak havoc on the new system. In the industry, we call them gremlins. Even something as simple as a temporary file could turn into a long-term problem for the new upgraded OS. Left-over kernel codes could wreak havoc on driver files. There are a myriad of things that could happen.
For example, in one of my PCs, I was lazy and so I upgraded from 7 to 8. Everything seemed fine at first. But 5 months in, my tiles started disappearing. I tried everything I could think of to solve this bug. Posted questions everywhere and worked with windows 8 experts. Nothing. I finally gave up and did a clean install.
With upgrades, it's a hit or miss. And problems may not show themselves until months later, when you already have tons of things installed and everything customized to your likings.
Just do yourself a favor and do a clean install at the beginning.
