It depends entirely on what you're going to do with your laptop.
At this point, a cMBP is more upgradable than the new MP. I'm a musician who needs to be able to change my mind about the configuration depending on the gig, and I need firewire compatibility.
Here' an example: For a coming gig, it's very possible I'm going to need two internal hard drives -- my 500GB SSD for my apps and a larger HD drive for huge project files and libraries. With a cMBP, I can remove the DVD drive and put in a 2.5 hard drive instead. When it's all over, I'll reinstall my burner.
Firewire is necessary because of legacy interfaces, drives and so forth.
Yes, the Retina screen is pretty and, yes, I'm nearsighted. I'd add the screen to the older config if I could. But as an Apple salesman (also a musician) pointed out to me when I was in the store, the ppi isn't as dense as on the iPad and the necessity isn't as great because I'll be looking at the screen from a greater distance. Besides which, I have the "Hi-Res Anti-Glare Screen," as it was called way back in 2012. Not as good as the retina, but also not quite as shiny.
Ultimately, I have to be able to take my laptop apart -- especially since the new Mac Pro is going to be just as resistant to customization as the rMBP. So at the time -- and for the time being -- the cMBP was/is the only possible choice for me.
No point in dissing other people's choices. There are a lot of good reasons to get the retina model. But for my purposes, the 2012 non-retina version has served my needs better than the newer model would have at the time (late 2012). It wasn't a matter of money. It was a matter of necessary flexibility.