I notice that I favor my left leg too- yesterday, I was riding in the streets and absentmindedly decided to try using my right leg. I almost fell into the traffic, pedalled backwards and caught myself with my left leg.
Sadly, I do notice that my left leg is also slightly more muscular than my right leg too. It's a little more defined with muscle definition. I've decided to weight train each leg separately and to do one legged drills on my rollers this winter, as well as practice using my right leg more often. I hate to think I have a muscle imbalance.
Koffee