Absolutely do not buy the non retina MacBook Pro under any circumstance. I do not understand why Apple still sells it, but if you're on a budget, you can get a similar, if not more substantial discount on the retina models by checking out the official refurbished store.
I bought one 2 weeks ago due to my very specific requirements (well its actually a long story, my original 2012 was replaced under warranty with a Retina pro that didn't match my needs). The i7 model is about equal to the baseline Retina Pros in geekbench, but the retina pro has better graphics (though the retina screen probably does drain that a bit).
The retina pro also has a much better battery, though the non retina isn't *that* bad.
Essentially for those who want optical drives, certain ports, an IR sensor and the ability to expand the non retina pro is still a good machine, albeit an ageing one.
Apple still sells it because its a big seller. On Amazon UK its number 4 or something in laptops, ahead of the retina pro. In the US, its only one position behind the retina pro.
For my case the non retina pro works out. I was very happy with my basic 2012 model (I5) and now I have an i7 with a 1 TB SSD, and I'll be going to 16GB of ram in due course. Plus I have the optical drive and ports I need plus other niceties such as the IR sensor, the battery light indicator, sleep light and a NON touch force trackpad.