go with both
He is right about the increased ROM and there is more stabilizing muscles recruited, but you have to also use barbells. One thing is when you are FIRST starting out, your stabilizers aren't developed enough to use the weight sufficient to fatigue your major muscle groups! So you can't effectively overload your chest using dumbells alone, at first. One more advantage of barbells is most people can use more weight on barbells in most exercises, so you can overload your muscles easier! However, dumbells are extremely important too. You don't want to use just one type-both are result producing for different reasons. I'd try to incorporate a dumbell and barbell movement into every workout!
--New Guy