Music Production- Mac
Wav Proccessing
MIDI Proccessing
Sample Proccessing
Synth Emulation
Mac software runs far more foundational to the proccessor than PC format.
JUST AS AN EXAMPLE, it would be SIMILAR to a PC running in straight machine code instead of standardized C++ based software.
Mac software has very little margin for error in it's programming, and so the clock runs with great efficiency whereas with PC software, often times, errors are written in without choice just to perform one portion of a subroutine whereas the rest of the subroutine's functioning is not used. (some programmers call it proccessing fat)
Music Post Production- PC
Wav editing is much faster than a Mac.
Especially when it comes to inserts, simple copy and paste and SOME simple transformations (amplitude, Normalizations, and other post production dynamics.
I like mastering with the PC because it is pretty effortless. However, if a noise reduction is warranted at the material's end of proccessing, I will take it back to a Mac because it is capable of removing noise with "a finer rake" or higher FFT resolution without having to wait a week for it to finish up.
Desktop Publishing- either.dependant on program used. Ms Publisher XP does fine. I I Dont think people examine flyers beyond a hundreth of an inch, but if you have Adobe on a Mac you have 10X the accuracy of publisher (one thousandth of an inch). I say wtf, do you need that accuracy for a flyer? Overkill. Might as well build your flyer with AutoCAD LOL
Internet depends on the proficiency of the user. advanced, a mac. long learning curve to the in's and out's that the mac has capability of. If you are not into port scanning or web harvesting, that's good because it is not nice to do that. Average mousing browser's: Go with a PC for the net.

It depends on the task really.
You can't put a Mac inside a PC, but A G3,4,or 5 can run a software based PC from mac language. Hardware based, up to 8 PC's at one time effortlessly.

It depends on the task. You wouldn't drive a golf course in a Ferrari Marinello, and you wouldn't take a golf cart on the freeway (Anyone with some intelligence anyway)

Things change all the time, so next week, things might be different.