Argus is a barker. He barks to go out, he barks when the doorbell rings and he especially barks when I change from my work clothes into sweats because he know we're going out to play in the yard.
Callie barks once in a blue moon. The only time she has ever barked is at something out the window. We couldn't see it, but she stood there for about 15 minutes, letting out low woofs.