yes, it is due in part to the tire. Tires that are more thorn proof are by their nature harder. Harder casing, harder rubber, harder flat protector inside. It translates to a harder ride and less tendency to grip. They will also be more slippery when wet than a soft rubber road tire which will in turn have less flat protection. Good flat protection is a trade off against soft, gripping, easy ride. I would not corner on Marathon Plus the way I corner on Conti 4000s. It's just the nature of the beast and you learn to live with it or try another tire.