physics is not my specialty but every study I have read indicate that tubeless tires offer lower rolling resistance than a typical clincher tire with a tube. from what I gather there is friction between the tube and the clincher tire which increase resistance. also the ability to run lower psi actually lowers resistance unless you are riding on perfectly smooth surfaces. most manufacturers are going to a wider tire on road bikes which allow wider footprint and ability to run lower psi for this reason as well as a more comfortable ride.