I can only say what my experiences from the past teached me:
Macs for a long time seemed (or SEEMED, as Kool Musick would've said) to be
the more stable choice.
By myself I had true nightmares configuring a PC as an audio workstation
back then (like 4-5 years ago). But then, I was running a buggy version of
Cubase with an audiocard that doesn't deserve the name (a way too expensive
TerraTec EWS64), no proper drivers until now.
But then, in the meantime I am on my 4th audio machine (well, one only was
some refreshed older one), and the last three machines all worked pretty
well.
So, if that was one part of your question: Yes, it is possible to build a
reliably working audio PC.
I highly recommend looking at some recommended hardware though. Also make
sure the mainboard and chipset is no crappy cheap stuff. I would stay away
from stock PCs, one should rather rebuild a one other persons are using
sucessfully.
In teh end, if necessary, I can use my machine in a professional environment
any day, I'm sure it wouldn't fail or crash more than any other machine
(Macs included). Actually Logic hardly ever crashes on me at all unless I'm
testing some new stuff, such as weird VST plugins.
Also, so far PCs offer more computing power, especially for the money. But
then, in early spring there seems to be a new 1600mHz Mac (don't know the
exact figures) which should really rock. Personally I wouldn't like to even
think about the price though...
In the end I think that Macs still *might* be a slight bit more stable
statistically, but that might have to do a lot with the fact that it seems
to be a common PC user habit of stuffing the machine with all kinda funny
hardware (such as cheap and crappy soundcards) and to install every stupid
little freeware app ever.
If you try to stay away from that, buy quality hard- and software, there
should not be too much issues when going the PC route.
I build a number of PCs for friends, from relatively low cost ones to pretty
much high end machines and all of them are just running fine.
Sorry if this sounds a bit PC biased, but I simply don't know enough about
Macs to say anything (be it good or bad) about them.
Regards,
Sascha