Either one will work great, either one has multiple software options. Pick the one you like better, or failing that, figure out whether one has better options for you (e.g. if you like one operating system better, if you are cost conscious, if you like the design of one over the other...)
I have both, I track on both, and there is no friggin difference quality wise. Money wise, the PC was a lot cheaper, and can be easily upgraded over time. But the Mac hasn't run out of steam yet.