budget id say is the biggest issue. currently i have a macbook and an intel imac and have a protools, logic and reason set up. i do most of my editing and self recording at home on the imac, however, i take the macbook with me when im recording a band elsewhere. the plain run of the mill macbook holds up fine, until you start using 10 or so plugins and are recording 8 tracks at once (drums or something).
if youve got 2K to spend, will be using it through college and portability is an issue, i would go with the macbook pro and throw at least another gig of ram in it, and you will have no issues.
you didnt mention what program and interface youll be using. some interfaces out there limit you to how many simultanous tracks you will be recording at once. if its 4 or less, you shouldnt have any issues with even a stock MBP. if its more, an upgrade in ram should do nicely.
if portability isnt an issue, a powermac and mac pro will do great. i would simply recommend buying an imac and spend the rest of the cash on whatever else you might need (mics, xlr cables, interface, programs, etc). and have you seen the 24 inch imacs? wow. thats all that needs to be said. good luck.