You probably will notice a difference although, I'd think that anyone on a tight budget such that they're considering Kumhos on the front and GY on the backi probably doesn't drive the car hard enough to ever notice the difference. So, in practice, you'll probably be ok.
What you might notice, if you ever actually need the run-flat feature, is that only the Goodyear meets the run-flat specification GM set for the car. The Kumho does not. Further, with Kumho, you get what you pay for. The Korean tire industry is not advanced enough to provide buyers with effective run-flat technology, so what Kumho does is add some sacrificial material to the inside of the tire which is consumed during run-flat operation. That makes Kumhos a "one-time" "run-flat" which must be scrapped after any run-flat incident regardless of distance.
For more on run-flats see: