Sugar already had a chip from Avid, so I just updated the info when I adopted her.

I "think" there is a difference. With Home Again, they send out emails or some sort of message to all the places which use their product, if you report your dog missing. With Avid, I think you just rely on the rescue, ACO, shelter, vet or what have you, to scan for a chip when someone comes in with the dog.

I don"t know about ResQ or any others, how they work.

My vet clinic has one scanner which reads both Avid AND Home Again. It is put out by a third party company.