Originally Posted by
pinniped
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.
Good points, though Marriott points may be redeemed at a decent CPP value if done carefully (e.g., 5 nights for a Category 6 resort at the PointSavers level). Also, MR points may be converted to airline miles 1-for-1 when done via a Travel Package redemption. Even with these techniques, you're right that you typically get a better bang for the buck with the SPG branded Amex.
One other thing to consider is that obtaining too many elite status levels means you are inherently diluting your use of each. For example, if you have status with Marriott, Starwood, and Hilton, each time you stay and utilize one, you are passing on the others. If your usage patterns permit, it might make more sense to concentrate on just one or two airlines or hotel chains and use them as much as possible.