I agree with just about everything above except for the implicit assumption that you have to decide on just one card.

IMHO, get several. SPG Amex is a good start--and remember you can get the business card as well, both personal and business have 25K bonuses at the moment. Or, to avoid the annual fee, you can just switch yearly between the two, canceling when the fee comes due. Personally I am too lazy to do this as I get older but it does work.

I'd also get the Chase Sapphire Preferred and one of the various Ink cards for starters as well as a couple of Citi AA cards.

And, remember, spouse can also get cards in their own name. Spending 10K a month is nice but those 50K bonuses can add up really fast to free first class flights.