Maybe a good second dog. :) They are headstrong! But if they're your dog, they tend to be stubborn for you. Heelers tend to be good listeners with a never-quit attitude.
It depends on how you raise them! A lot of herding dogs can end up as chicken killers if not brought up to be gentle around...
If I had to chose between the two: Border Collie. I love that focus.
But I prefer (Australian) cattle dogs. :) A lotta dog, but a great jack-of-all-trades who loves you AND working. If you can't decide between the BC / Aussie, and you can handle the intensity .... maybe a heeler would be a...