I've picked glass out of a flak jacket Mondo (23c, totally slick road tire) tire that had been there a while. It had worn smooth and flush with the rubber around it, but it didn't reach the tube. I've had Nimbus tires and never had a flat, but I did tear the sidewall, so I'd go with the armadillo version. They're heavy, but the sidewalls are pretty beefy. I've been riding flak jacket road tires for a couple years now and only one long fat thorn has made it through. I've had other flats with them (pinch), but only one puncture that I can think of.