There is a definite difference in the composition of the wheels. The earlier wheels were brass turnings the later ones appear to be bronze. Clean wheels and track are a must. Some have recommended burnishing the tops of the rail to polish and smooth them to reduce the accumulation of black gunk that occurs from the visible and non visible electrical sparking.
Pick up in my opinion between the different wheels is the same as long as they are kept clean. You can also minimize blinking lights in cars by keeping their wheels very clean.
