Around here microchipping is helpful but not enough.. I don't know why it is but none of the shelters and few vets scan for microchips on dogs that come in. I shudder to think how many dogs are adopted to new homes that could have gone to their original homes if only they had been scanned. When I worked at Petsmart one woman came in with her lab and I was talking to her about him. She had just adopted him and taken him to the vet, and the vet had discovered two separate microchips. I don't know how that's possible, but it's possible that he had been at a shelter more than once. The woman thought he had been microchipped, gotten lost or abandoned and wound up at a shelter, adopted, microchipped again (how could a vet not check before chipping a stray dog?!?!), then somehow wound up at a shelter again, and then she adopted him...
It drives me crazy, because the vets really push the microchips because they're such a lifesaving device, and then some don't check for them on stray dogs.. Because of that, I'd say microchip and make sure he's wearing his ID collar..