thank you for your response, there's three things, first i have a pretty good relationship with my attending (he's said multiple times he would want me to attend his program, but he doesn't have the weight to pull me in), second i don't think the chair has the time to write me a recommendation and he barely knows anything about me so i would rather not get a non-personal recommendation from him, so its really between getting him to cosign my letter or nothing at all. Finally I think that my attending has a good relationship with the chair.
thanks again