Processing speed and dealing with an industry that believes only Macs
can produce the files they need have pushed me to the edge.
As one who spends equal time on both platforms
and one to whom photography is important, I'd
say you have to go with a Mac because it's simply
too much of an uphill battle otherwise. Additionally,
the Altivec instructions in the G4 processor make
this the current machine of choice for Photoshop.
Virtual PC 3.0 should be able to run XyWrite fine and
should take care of minor keyboard problems that
existed with earlier versions of VPC. (VPC 3 also
reportedly runs ATM/Win95 fine, which VPC 1 did
not, but I have not yet tested it myself.)