Slow clap. Part of the reason why road bikes came with 19-23mm tires pumped up to 120+ psi is because they felt faster than bigger or softer tires, and because of flawed test methodology (testing tires on smooth steel drums in a lab vs. testing on real asphalt). I've heard a lot of people in the tire forum say that radials roll slower, and they certainly might. But until I see actual test results using a methodology that makes sense, I'm going to assume that no one knows the answer to that question.