I run PC at home(2 laptops, 3 desktops), I use a PC at work due to Onyx rip and our prepress is full of macs and a couple PCs, our server is PC based. All design work we do is Adobe or Quark, all on Macs, prepress hates when customers send in PC adobe files as they are never right.
I love my PC for the ability to work on it and for the fact that its all Ive used for the past 15+ years.
With that said, when I buy a new laptop, it will probably be a Mac book Pro. Im working on trying to get a new mac with parallels and windows 7 for my production computer.
To me, the overall use is the same. They do the same job that is requested of them. The GUI is a little different between the two, but with W7, its seems closer to a Mac than ever.
I have 2 wireless printers at home, a lexmark and an HP eprint, I hate the fact that the lexmark will work on the XP computers and cant get the drivers to work for the Vista laptop or the Windows 7 Desktop. The HP works great for vista and W7, but is finicky for xp due to the hardware requirements.
I feel that the Macs are a little more "efficient" than the PCs are. At any point of any day, I could be using either in prepress to prepare a job before sending it over to wide-format.