You can time the Amexes right so you can alternate years and keep perpetual or near-perpetual status.

Probably true for the Marriott card as well - the only problem there is that the Marriott card is a terrible "general spend" card. Its power is big earnings (5 pts/$) at Marriotts - and if you're spending that kind of jack at Marriotts you're already well beyond Platinum range.

Both of the hotel Amexes yield good general spend rewards, so if you want those two statues (SPG Gold and HH Diamond), you really aren't giving up too much in terms of opportunity cost vs. your favorite airline card.