Weight does not necessarily proportion to speed, especially in boxing :D
 Ray has had boxing as his focus for over ten years of his life. Plus, technique is only part of the speed. A good deal of it comes from muscle that Nick has not had the chance to build up yet. 

In any case, knowing the theory of boxing or fighting or how a person moves is useless once in the fight itself. Fighters have spent years studying each other, and in the end they still end up having to improvise on the go. If learning how to fight was all a person needed, then there wouldn't be anymore knockouts, and what fun would that be? xD