I disagree with your sentiment that the default upgrade install is more dangerous. If it was so, I don't think Apple would have made it the default. It works well for most users.
I did what John Gruber and many more seasoned mac users suggested: make a backup of your mac contents and do the default upgrade - if it fails, then go on to the clean install with your backup, nothing is lost. If it works, you just saved yourself a whole lot of time. I had Leopard running on my computer in 50 minutes with this method and I'm as happy as I can be.