So retina's not important unless you really want that resolution, I would definitely recommend researching your pick, some specific models scattered through are a mess for things like hinges breaking, I would of course recommend that if you make sure you get the fully supported i5/i7 and not the 2C/4T, while they aren't bad, the price difference wouldn't be much for more physical cores and threads, I have a 2012 edition myself with 2c/4t its still working fine with newest OSX, but its starting to get a bit less snappy(Sierra uses a lot more memory than older OSX's) I would definitely recommend getting more than 4 GB ram if you're wanting to run the latest(El Capitan will run fine with 4), I mean a kit of 8GB is only like $50, just make sure to research the get ram with the right timing and speed, or else it might not work with the laptop.
Here's a link of a website that documents mac editions fairly well, not sure if links are allowed, if not please remove:
http://www.everymac.com/systems/apple/macbook_pro/index-macbookpro.html