Thanks for the additional information. For 95% of everyday use, you wouldn't see any difference in performance. For the other 5%, like Logic and/or movie editing, the difference would still probably be unnoticeable. The .2GHz is not noticeable at all. The biggest difference between the two would be the graphics processing:
2012
NVIDIA GeForce GT 650M
512MB GDDR5
2013
Intel Iris Pro 5200
Up to 1.5GB shared from main memory
The NVIDIA is a discrete graphics chip - the Intel Iris Pro is built-in to the processor. For gaming, the NVIDIA would be better. For all non-gaming/3D applications, they would perform about the same. However, the Intel Iris Pro in the 2013 does reduce the amount of the 8GB RAM available for applications.
If it were me, I would probably go wth the newer 2013 model, as I am not a gamer. The graphics processing has no effect for audio apps like Logic Pro X, and minimal effect on iMovie and amateur use of Final Cut Pro X.
Of course, it's really up to you and your budget.
Hope that helps,
C