I am starting protection training. Is it a hindrance to the dog to have on a agitation collar vs agitation harness?

I would use a harness simply because the dog is not going to be putting pressure on the neck area while learning the bitework skills. They are more comfortable in the harness and breathe easier. I also like to “preserve” the neck area for later finesse obedience training. By allowing dogs to pull into a collar too much you are desensitizing that area for future work.

I hope this helps,
Cindy Rhodes