It's kinda like asking what's better, screwdrivers or hammers? It depends. Both have their advantages for different exercises. With the dumbbell, you often get a longer range of motion, a more complete muscle-contraction and can work on the small stabilizers. In addition, if one side is stronger than the other, you can train one side to get back on track. But as mentioned, a bit more tricky to progress with and you generally can't use as much weight as you could with a barbell. ~ Berceste