I have experience of both, but am (now) a biased Mac Freak.
The great thing about Windows is its universaility - everyone knows how to use it, there's a massive pile of software for it, everyone at work / friends use it etc. etc.
That's good. It means prices are low and accessory hardware is available / competitively priced.
However, it also means the platform is a target for virus writers and spyware which is a boring pain. It also means the hardware you might find inside any two PCs can be very different (sound cards, graphics cards etc. etc.) and sometimes incompatibilities in drivers can cause problems.
I spent years building boxes, troubleshooting, rebooting. In the end I had enough and got off the roundabout. Bought a Mac and have never looked back. It's a very different system, which might take you a little while to get used to, but I love it. Stuff tends to 'just work' more for me on my Mac than on a PC - ie. I spend more time using it and less time f**king around with stupid settings. Also, the Mac is highly optimised to messing around with multimedia - images, video, sound. It's a doddle to import and share images from a digital camera and I understand the movie / DVD stuff is fab too (I'm a stills man myself). The iTunes / iPod integration is (perhaps not surprisingly) even better on the Mac than the PC.
I sent my dad a link the other day here which was written by some heavyweight computer blokey who just moved to Mac because he was also so sick of the security weaknesses.
There is a dedicated portion of the Apple site for 'Switchers' here .
You might want to visit the Apple store on Regent Street for good advice and all round glitz.