I swear that in a manual on tennis published by the German Tennis Association (Deutscher Tennis Bund) it stated as fact that all things being equal a ball will move more from left to right than from right to left if spin is applied. Could this be true? I no longer have this manual published 14 years ago but it always struck me as puzzling.
I'm not sure what he meant by that but he could be referring to an aerodynamic effect. The rotation influences how air flows around it, creating forces, just like lift in a plane. See, for example, Magnus effect: http://en.wikipedia.org/wiki/Magnus_effect Of course, the direction of the curve isn't necessarily 'left' but it depends on the rotation.