I don't know if people are thinking through a dog versus walker battle.
Typically, a canine's attack is designed around causing enough damage that the victim weakens due to a loss of blood. Also, when a person is attacked by a dog, most of the victim's efforts are defensive, in trying to block the attack in some way.
A walker, on the other hand, will not take a defensive stance. Since we have seen them eat a horse, we can assume they will eat a dog should they get a hold of one. So a dog attacking a walker will meet an active attack.
The walker will try to grab and bite the dog until it's brain is damaged, or the head is removed from the body. There is no weakening from a loss of blood, and even spilling the guts won't slow it down.
And living animals have an instinctive fight or flight instinct. Since we haven't seen zombie animals, I don't believe a dog will turn from the bite. But if the dog takes enough abuse, it may retreat. Then you have a dog that may bleed out on its own and a damaged walker following it.
I would put one dog against one walker at 60/40 odds, in favor of the walker.