Mia,

What a fantastic post. I've been lurking for a while and have much respect for your insight. It helps to see this less as a card question and more as a rewards program comparison.

It looks like the standard Membership Rewards from Amex is the weakest offering for me - it is less widely accepted than Mastercard and no bonus for stays at Starwood hotels.

Starpoints look more fungible with other partners and programs than Diners Club does, plus there's that nice bonus.

I think I'll cancel my freebie Amex, get the SPG card, and keep my Diners as backup where the SPG Amex is not accepted.

Thanks so much, mia!!