Cost comes to mind first. Second is....you say they have computers everywhere, but do you really need portability....if you do, or if you think you EVER will, then you have your answer. The MacBookPro. I have an iBook so I think i'm going with the iMac.
Another thing that comes to mind is HD space. You can get 250, or 500 with the iMac, or not so much with the MBP. With the MBP you might need to get an external HD. Do you want to ever play games? If you do, and you're like me, I hate playing games on laptops, it just doesn't work for me.
Hope that helps some.
Jack