Well, I’m not the best person to ask this, but…
I suggest you visit http://www.macworld.com or visit the message boards at http://www.maxfixit.com . The friendly people at MaxFixIt can give you all their reasons why Macs are better for music. OK, I’ve been clever and I have the direct URL for MacFixit’s boards (but check their home page too 
http://www.macfixit.com/cgi-bin/ultimate/Ultimate.cgi?action=intro True, MacFixit is a pro-Mac place, but they also will know more things first hand about music and Macs. AND some of them have been cross-platform, worked in both PCs and Macs, and can describe the differences. I cannot guarantee that they will help you out as much as you’d like, but they are worth a shot.
All I can tell you is that Macs seem to be more innovative in such things as graphics, art, video and music. Look at the newest iMac DVs. I can also tell you, as someone who started in with computers about the same time you did (2 years) that Macs are not that scary. They are fun, and easy. You can find an old PowerMac on eBay for a few hundred bucks. And used iMacs are in the $600 range on eBay.
I also can tell you that many musicians use Macs. Strength in numbers. I also have heard (though of course I don’t know first hand) that with things like graphics (can’t speak for music, but suspect it’s the same) that most of the “Big” art houses use Macs. If you were to bring in a PC disk to them, they’d give you a funny look, maybe not take you seriously, because everyone uses Macs in their field. Now, this is just what I’ve heard, but if it’s partially true, it makes you want to expose yourself to Macs, doesn’t it? Can’t hurt.
You seem open-minded about the prospect of using a Mac, so I am confident that you’ll come to the right conclusion for you. Which may not be a Mac, it may be a PC. But, don’t listen to these rabid anti-Mac people (they’re out there) they often hate Macs for reasons that are not applicable to your needs. (i.e. Macs may not be tops for games - do you intend to use your computer as a gaming machine? If not, who cares if Macs arent’ better in games!) And, some people need to get a life, and just hate Macs because they hate them. (And, there are Mac people who hate PCs too - sure.)
Well…hope this helps.
Polydactyl Cats Unlimited
“A Cat Cannot Have Too Many Toes”