This is a debate that has been going on for years and would probably still be going on years to come.
Saturday 24th January marked the 25th anniversary, when the first Macintosh was released. If you use Mac now, you obviously think Mac is better than PC. The Mac operating system - Mac OS X, is arguably the more elegant of than PC. Although vista is trying to battle back, i still think that the Mac interface is prettier and more intuitive than any flavour of windows.
Mac users could list various reasons why they feel Mac is better whilst PC users could list the same for Windows (chech out The Gadget Group discssion on facebook http://www.facebook.com/photo.php?pid=5484925&op=2&o=all&view=all&subj=7855383410&aid=-1&oid=7855383410&id=519025516)
At the end of the day, which one is better comes down to how you want to use your computer.