I don't think there's really much difference in using maya between macs and pcs (except some shortcuts)... so it really comes down to budget and preference. This isn't the place for yet another mac vs pc debate, but rest assured that there are many people here that are happy with macs and others that are happy with pcs.
Make a list of what software you want to run, and check compatibilities for mac os, windows etc.
Check your budget against the available mac platforms, and see if that gives you what you want. (You can get a PC for any amount of money generally). As for specs, do a search on the forums, since there's a ton of info already. If you have a specific question, feel free to ask.

Hope that helps.