For me, the GP4000S has been more flat-resistant than the Gatorskin. They (the GP4Ks) get plenty of surface cuts, but the glass doesn't seem to get through the vectran layer or cause an issue. I don't run them all that deep compared to other here, but they don't succumb to cuts in my experience. The Gatorskins would occasionally fail to a sliver or thorn. Take that anecdotal account for what it's worth, but to me, I run the GP4K and enjoy better tires with fewer flats than the Gatorskins I used to run.