Thinking of purchasing a MacBook pro. Prefer the 15" since it is quad core. However, not sure if the duo core of 13" is good enough. Would like the late 2013 version with Iris or Iris Pro. I am seeing some in the certified/refurbished section of the Apple website. Can you share with me any experiences, good or bad, on buying one of these versus a new one? I will need to mainly use it for photo editing and graphics design using the Adobe suite of products. Will the duo core and Iris suffice or should go for the quad core and Iris Pro? Thank you.