I have been riding on Marathons. I ride strictly rail trails, with some of those trails being asphalt. Just bought a Trek Verve that comes with the Bontrager 700x45 tires. Rode the bike 40 miles, and I hated the tires. Put 700x38 marathons on it, and I couldn't believe the difference in how the bike rode. Just felt faster and lighter. I really didn't notice any less of a comfortable ride with the 38s on. So yes tires do make a difference.