First, PCs have a tendency to have problems that are very inconsistent. I remember reading one of Peter Norton's books discussing troublehooting a PC and him mentioning how you can have two identical computers with identical software, and yet one not work. I discovered it in the field. On a PC, your only choice is often to actually uninstall the suspected culprit or reinstall the system. And here, Macs also have an advantage.
Macs are easier to install, upgrade, and set-up.
There are PCs that aren't bad. I love it when a client buys a Dell. I just sit there and wait for everything to install. Of course, on a Mac everything comes factory installed, you just turn it on, there's nothing to install at all, but I guess with PCs its safer to have archives that uncompress before the first use. But the real issue is upgrades.