Now that's a dam good question. A few powerful punches will put a guy down quicker but many fast punches will keep them off balance, overwhelmed, on the defensive, and it will be easier to nail them. I guess it's just a matter of personal preference and body type, attributes, etc.
Member of DaJoGen MMA school under Dave Hagen and Team Chaos fight team under Denver Mangiyatan and Chris Toquero, ran out of Zanshin Martial Arts in Salem Oregon:,