I think that highly depends on the subject at hand. In some cases, it's better to be slow and steady, focussing on the job at hand and not let your impulses to go fast take over. Sometimes the reward will be better this way. Other times it's good to go fast - faster than you've ever gone before. Sure, the high squeals it might produce can alarm your neighbours, especially if it's in the middle of the night, but nothing beats a good nightcore session. Most of the times, though, you need to find a healthy balance between both speed and stamina. Slow and steady does win the race, but might get dull. Spicing it up here and there with a nice, fast, flowing motion might just be enough to spark things up leading everything into an orgasmic finale, rewarding you with both a big pp and satisfaction.