Uni wears a breakaway cat collar with her tags on it. it also came with a bell which is good so i know where she is all the time without having to actually *look* at her, I can just listen!
But for walks, yes harness only!
Also Uni has never gotten caught on anything before, EXCEPT when we were teaching her how to play basketball. Her collar got caught on the rim of the hoop and it scared her a bit. So we went back to "training" with out it on, and now that she knows how to play, the collar stays on.