well, technically, the reason we use the lowest number is to give credit to the one who was here first. there's no avoiding redirects. any merge or rename will redirect.
and google doesn't care about the number of redirects, its our own server. each url request has to be looked up, then if it redirects, then that one has to be looked up, etc... the more lookups (redirects), the more strain it puts on our own server. so we want to minimize duplicates, in order to minimize the number of redirects.