It's really pretty meaningless. It barely even shows up in benchmarks, which tend to be exaggerated compared to real use. If you're concerned about power, a 2012 15" refurbished model is still far more powerful than either if you can make use of that power. This is just a splitting hairs thing, and yet people still assume it will make a difference under certain workflows. If I put them side by side, I don't know that you would be able to tell which was which without a benchmarking tool or the use of "about this mac".