Difference between MacBook Pro 13" Early 2011 MC700LL/A and current model 13" / 13" retina?
In my opinion, I'd get the newest Mac, especially if you get a warranty with it. The newer the computer, the more OS X updates it can handle. As far as graphics go, I'd go with the one that has better specs. If you do end up buying a new one, upgrade the RAM, and if you plan on working with video editing software, definitely get the i7 processor instead of an i5. I currently use a Mid 2012 MBP (Non retina) and it functions pretty well, however, there are times when rendering videos gives me the "Spinning Wheel of Death". The new one is going to be better, even if it's a little more. And as far as your statement about the "Macbook Pro hasn't changed much since 2012", the new ones are lighter but don't include disc slots, so keep that in mind. The new MBP is definitely an improvement, and although the looks haven't changed much, it'll (most likely) run smoother and gain more support for future updates.

EDIT
If you can (I haven't bough a new Mac in a while so I'm not sure you can do this with laptops), upgrade your graphics card to the Nvida (whatever model they have). It helps a lot with 3D animation and graphics.