MacBook Pro Retina 13" or 15"?

I am looking to purchase a retina MacBook Pro as my first Apple machine, and I am torn as to which model I should jump for.

I would buy either the 13" or 15" retina (both base model) as refurbished in order to save some cash. The 13" has a reduced form factor, and is ~$500 cheaper than the 15" refurbished retina in Apple's online store. However, the 15" does have increased storage, faster gpu, and a bigger processor.

I have read in numerous places that the 13" has trouble processing the large resolutions of the retina screen at times, and users can experience slowdowns even when browsing media-rich web pages; for this reason I have been somewhat shaky to leaning towards the 13", but with the recent price drops it has become much more attractive.

I would use the computer primarily for programming, running VM(s), networking, web browsing, video streaming (netflix, youtube), word processing, and such. I already have a powerful desktop PC for gaming, but I might be interested in some LIGHT gaming every now and then on the MacBook. I figure that either machine could accomplish these tasks, but if the 13" retina's gpu is constantly playing catchup with the display, then I am curious as to whether or not I should just spring for the better 15" model for an extra $500.

Sorry for such a long post, I am just a little wary of making a >$1500 purchase.

Thanks Apple Core!