Energy is more important.
Whether you like a slow and heavy round, or a light and fast round, you still want a high energy round.
Low energy rounds just suck, like a 35g .25 auto from a 2" barrel, which will only give you around 60 ft. lbs. of energy.
Or a 60g .32 auto from a 4" barrel, which only give you around 120 ft. lbs. of energy.
Compare that to a 200g .45+P from a 5" barrel, which will give you over 500 ft. lbs. of energy.
Or a 125g .357 magnum from a 4" barrel, which will give you around 580 ft. lbs. of energy.
Or a 155g .40S&W from a 4" barrel, which will give you around 500 ft. lbs. of energy.
High energy rounds are just more effective than low energy rounds (when it comes to quickly stopping aggressive humans) regardless of the velocity, IF the bullet stays inside the target and dumps all of its energy in to that target.