The speed differential between a fixed bike and freewheeling bike probably makes more of a difference than anything else. I rarely exceeded 25 miles per hour on my fixed bike and would often pedal down hills closer to 20 mph as that was something I could sustain with backpressure without needing to use my brake. Those same hills on a freewheeling bike easily see 30+mph and most of my rides include at least one hill of closer to 35-38 miles an hour.