We picked wolfie up a harness and he loves it, although he thinks he can pull with it so we are going to have a few re-training sessions with him on it, but it shouldnt be an issue. he seems more comfortable wearing the harness, the collar always seems to bug him.
if your dog doesn't pull (hooray for that!) then I think a collar would be sufficient. It's easier to put on anyway....haha. Harnesses can be uncomfortable on dogs, they can rub and cause wounds. I have seen this on a friend's dog and it looked painful. On the other hand I Have never seen any chafing problems with a regular nylon or leather collar. Good luck with your choice!