One more positive to spinning: it helps in recovery for the next day. Mashing takes more out of the legs. It's my belief that this is really the main focus of road pros. It also leads me to believe one way is not better or worse than the other for most non-pros. People in the road forum debate the pros and cons endlessly. But unless you're doing multi-day stage racing, it's almost a moot point. Do what works for you...some are spinners, some are mashers.