A straight upgrade is the safest, least disruptive method of all.
I don't buy the argument that a clean or archive install goes anywhere useful in terms of troubleshooting incompatible applications. If by chance you've got an application installed that doesn't work with the new OS, you're going to discover the incompatibility when you reinstall it anyway, and you would not know about it until you did reinstall it. Nothing is gained, as nearly as I can tell. Incompatible applications aren't a big deal anyway. They should not be able to crash the OS. If an application doesn't work in Tiger, it might need to be upgraded, is all. You can even do that homework before you upgrade OSX.