If you are actually going to walk, I suggest a harness. Pulling on a collar can be damaging to throat/larynx. imagine wearing your collar buttoned all the way up and a tie. Then, someone grabs the end of your tie abruptly and says "Hey! Over HERE. " Wouldn't you rather be guided gently by the shoulders?
We have had one lil girl that we lost to collapsed larynx complications. This was a genetic issue. We have recently lost another to degenerative myleopathy. Both conditions could have been worsened with the use of a collar for walking. Emma doesn't even have a collar. Her tag is on her harness. I'm a huge fan of microchips too.