I'm neutral about the pet policy.By law, service animals are already allowed on all trains. They are not in carriers, many are larger rather than smaller, the world as we know it has not come to an end. If proper rules are enforced, this will be a non issue. Let's see Amtrak get through a week without a rental freight engine pulling in a train before this is considered important.
As to service animals vs pets, legitimate service animals are well-trained, pets not necessarily so.