I have both and I'll tell you that I've been turned off by both. The mac and waiting for audio to be done on osx drove me to go back to hardware solution for sequencing. It's only now that drivers have been completed and software is beginning to surface; I'm impatient and they really took too long. They were more concentrated on the video people (that's honestly my opinion and many others in pro audio) It was hard because os 9 was very stable but apple's ceo put it in a casket and crammed x down everyones throat; you can still boot to os9 but support has all but disappeared. X is a god send and the code for audio was so drastic in change that the companies didn't go along with developing at the pace apple was forcing them to. Then when some companies jumped on at osx 10.1 apple went and changed it yet again with osx 10.2 jaguar. That's when I said f--k it! It's a great web design tool and is my main video editor for my boxing legend archive (i have bouts from the last 15 years) and this mpc 4000 video/dvd that I'm making an attempt at. They lost my faith as an audio professional.
The pc on the other hand never changed. No forced upgrades with new OS; continued support between os's with most manufacturers. And yes you can run a full blow pro tools 24 mix system on a pc. Go to
www.digidesign.com; I kid you not. The user experience on a pc takes a great deal of patience and really good know how when it comes to resources and driver conflicts. This is what detracts from doing audio on this platform; if you do however have the patience; you can manage a flawless multi track/midi/sampling computer workstation.
If you are patient and have a bottomless cash pocket go with the mac; I just didn't have the patience to wait and I refuse to stick with a platform that will force me to change my OS and abandon support if i don't. I can tell you that web design and video editing/authoring is sweet as hell on a mac. Apple acquired emagic and that can only mean good things as far as audio on the mac (too little too late for me) Pro-tools has gone x and so has steinberg; Motu is almost here (again this is two years too late - that's how long i've been waiting)
I'm getting a pIV motherboard for the pc and it will remain scsi based and audio only; no internet/video/mp3 shyte. It ran great for me since 1998 on a pII 400 and I kept it audio only. PIV with Scsi (15000 rpm) will turn it back into a multitrack beast. I am looking into Mackie's 24/96 HD solution. I've seen them in many a studio and they run rock solid.
Do some research my man. I enjoy both platforms for different reasons.