A better question might be: "Given my goals of xxxx, what sort of training might best enable me to reach those goals?"

Some time ago I read an opinion by a physiology researcher, who said that human leg muscle biopsies don't actually show fast and slow twitch muscles. We seem to see evidence of that in athletic performances, but in his opinion that is the result of training and cardiovascular talent, rather than muscle type. This makes sense to me, witness the transformation of cycling gods from one type of performance to another.