My boys always wear collars with tags. When we go for walks, I use a harness on Bandit for many of the same reasons AdoreMyDogs gave for Cassie. It is much easier for Bandit's breathing when the harness is used.

Adore, Bandit is stubborn also but as with you and your Cassie, he always walks beside me or slightly behind me. He will not stray. I can't teach him to "sit" or "fetch" but he's a natural on leash. Must be something about the breed.