My experience doesn't match that. ISP DNS servers just return the A or AAAA record that they're asked for, and the return time is more or less identical for the

My experience doesn't match that. ISP DNS servers just return the A or AAAA record that they're asked for, and the return time is more or less identical for the two, not 4x longer. All of the client resolvers I've ever used wait for both records to come back, and your DNS resolution returns both sets of addresses. I think OSX does some sort of racing here, but it still gives v6 some amount of head start (~150ms?). Also, Google's published v6 stats say that 29% of their users reach them over v6. That doesn't seem to match with "you're almost always going to end up getting its ipv4 address".