PC is easier to build than a Mac.
With a PC you get much more compatibility between parts, motherboards, graphics cards and RAM.
While with a Mac,
almost all the parts you put into it have to be made by Apple
(Trust me, I've built PC's before and seen inside a Mac, it's easier to build a PC)
+ The only Mac you would be able to custom build would have to be a Mac Pro, since it's the only one with a tower.
The rest are pretty much like laptops of all in 1 pc's which are REALLY hard to do...
Unless you were talking about making a PC, then hacking it to operate on OSX (Then it's easy)