I usually try to shy away from the ole Mac vs. PC debate...but the best case for me was to go with both! Call it a 'hybrid home studio' if you will.
There's advantages with both (as everybody has been saying). As I'm writing, it's on my Mac. I don't dare go on the internet with my PC these days! lol
But ---> I do use both systems for pro audio. The mac is more stable, there's no doubt about it. As far as sound goes though, I personally cannot tell a difference. In all fairness, my preferred software is Sonar and Sound Forge with the PC....cakewalk has come a long way from a few years ago.
Remember, you can build a really really powerful PC for pennies compared to what you'd be spending on a high end Mac....plus building your own PC is fun (in my opinion)
My mac is more user friendly and I've never really had to worry about a virus, you just don't find that kind of thing on Mac OS the way it is with PC's but it all goes back to the whole 'supply and demand' thing.
I just think it's important to be skilled on both platforms these days, it'll teach you so much patience.
by the way: I've seen plenty of people using Emacs and older Imac DV's for pro audio, they work great! The only problem is that you have to use a firewire interface (no PCI slots)forget about recording via USB. the Emacs are espescially nice (and cheap!) RAM upgrade is easy and firewire hard drives work fine....but that's just my opinion.
hey, if Trent Reznor can record "Pretty Hate Machine" in a hotel room with cheap mics, drum machines and a 4 track then you should be ok with whatever platform you use
good luck!
Adam