during the base period in cycling, which is more important, time on the saddle or the kilometers that you log? i know these two go hand in hand, so that means when you're out there riding for hours it means that you are also adding mileage BUT my question is specifically which is better, riding 4 hours at ave 20kph or riding for 2.5 hours at 25-30kph ave? which of the two is a quality workout?

hope someone can shed light...thanks!