Most people seem to be proceeding on the basis that credit cards are for the sole purpose of accumulating miles. But that model certainly doesn't work for me. I'm rather surprised that it works for anyone.

I think clearly the SPG Amex is the most flexible, and they seem to offer enough promos to keep most people happy. But my Amex Platinum card offers me access to several hundreds (perhaps a thousand) different lounges, gives me upgrades and companion tickets, 15 days out of country medical coverage, no hassle rental car insurance, priority check-in throughout one alliance as well as on a number of other airlines, a number of "priority security lanes", and so on. It also let's me earn points on several different airlines.

Yes, it SPG might earn more points (effectively) on more airlines. But as frequent flyer for the last 16 years, "free flights" don't really appeal to me.

I think it's a bigger question than just which credit card get the most miles.