13 inch Retina or 15 in Retina

Hi guys,
i'm looking to invest into a MacBook pro.
now the question is should I get a 13inch or 15inch macbook pro retina.

I travel a lot but I do watch movies most of the time on my current ipad, or desktop.
I would probably use the following software most of the time

-Microsoft Office - Word and Excel
-Internet
-Youtube
-Netflix
-Picture editing
-Adobe Acrobat
-Occasionally: AutoCad
-Occasionally: Microsoft Projects or P6 (apparently i can run it in parallels)
-Occasionally: play a game (Assassin's creed)

Ideally i'd like it to be able to carry it everywhere when I go around to the gym, coffee or GF.
I was hesitating on the 13inch but it seems that it wont' be enough space. I have not seen any of them in person. But I would like to have a decent Laptop with which I could do my CPD, watch movies and some work sometimes.

Mac

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