I voted a little bit of both for both of mine. Dixie is only hyper when there is a dog around who doesn't understand she is the alpha in the crowd. After she makes her presence known, she is the most mellow dog around and is very happy to oversee all the activities as she chews her sticks. Of course if everyone knows from the start she is queen bee, then she's mellow all the time.

Dusty is always mellow except when another dog tries to take his frisbee away. When we go to the dog park, I have to hide the frisbee from his site so no squabbles will break out. If he doesn't see the frisbee then he doesn't care and just plays with the other dogs. He is a frisbee nut! Usually where you see Dusty, the frisbee is not far behind.