I use a harness and I believe on smaller dogs you should:
When Daisy was a puppy....she was my first small breed dog...I had a collar on her I was at a pet store and some woman freaked out on me bc Daisy was in a collar so I asked her what her problem was and she told me that I could kill my dog with a collar and that she should be in a harness. I was uneducated and glad that she told me about it but what really troubled me is my vet never said anything to me that Daisy should be in a harness and not a collar
I am so glad for that outspoken woman!! lol