Hi Christopher,

Actually I choose laptop because I am a Phd student and everyday I should take it with my self to department and home and also because I am in another country and when I travel to my country a lot! so I need to take all my data with myself that is why at first I choose laptop and then Mac (because Mac is more light). 
I want to do my phd project in the area of image processing with machine learning approach so huge data I have and my most work is with Matlab software and that software which you mentioned like SPM and Freesurfer ,... I never had Mac and my previous laptop was SOny (I have had this from ten years ago and still it works good but the problem is it is really heavy and nowadays it has a lot of noisy vioces :)) )
As I try to catch more information from Internet Mac Air is like tablet, yes? and it is not possible to work with it daily for big data processing and it is better to use Mac pro... these are just my information and I try to get more professional info here because all you are professional in the work area.

Thanks
Vania