Your Sapphire Preferred card earns double points on travel (including public transportation and parking) and dining, definitely use it for those categories.

Your SPG points are more valuable than AA miles, as you can transfer 20,000 SPG points to 25,000 AA miles.

Your most valuable cards for everyday spending are your SPG Amex and your Sapphire Preferred. Definitely use the Sapphire Preferred where they don't take Amex. Really what it comes down to is what currency you value most: SPG or Ultimate Rewards. Lately I've been reading on a lot of blogs that people are emphasizing Ultimate Rewards points more and using Sapphire Preferred before SPG (The Points Guy and Lucky from One Mile at a Time are all using prioritizing the Sapphire card right now, but View From the Wing and Rick the Frugal Travel Guy still seems to prefer the SPG Amex. What is your next travel goal? Would you rather have more AA miles or UA miles or hotel points?

The Million Mile Secrets guy's strategy seems to be to churn as many credit cards for bonuses as he can manage, then put all his spending on his Chase British Airways card to get the free companion pass after spending $30,000 in a year.