Suped-up 13 inch or macbook 15 inch?

[iMore Question]

I am about to get a new macbook and am debating the costs/benefits of the 13 inch vs 15 inch. Much of discussion is benefit of 15 inch in terms of graphics and audio-visual software for content creators. My interest is more in how each model goes with heavy-duty computational software like SPSS, which I use heavily, often working on multiple open datasets. This program is what is causing me the most grief on my old macbook, which only has a 2.4 GHz processor, 8GB memory, 250GB SSD, and sometimes can't cope when I try to do complex processes and crashes. Both 13 inch and 15 inch model would be a significant step up, especially if I customise up to higher speed processors and storage as I intend to. Does anyone, particularly those who work with SPSS or statistical software, have thoughts on which to go with?

 

[TripleOne]

I would always recommend the 15 inch due to the specs and screen real estate.