Student Graphic Designer, looking to purchase a MacBookPro.

Hello! I am a graphic design student looking to buy a MacBook Pro. I am confused between the 13" and the 15" model. I noticed that the processors for both are different, Intel i5 dual core and Intel i7 quad core. Another criteria was the graphic card. I will be using the Adobe creative suite frequently. Both the models come with the Intel Iris card, but the 15" model offers a AMD Radeon card upgrade.Which one should I prefer?