We have 2 Amex Plats and 2 CSR's. When I travel, I carry them both.

I find the CSR travel credit to be much easier to use, as do most people, but hang onto the Plat cards for the Centurion Lounge. We fly primarily out of LAX, and eagerly await the new lounge opening. When we fly out of SAN, the Platinum cards get us into the small lounge also.
Now that the fees on both cards have increased, it's likely that one of the Plats will be cut from the wallet.
I do not maximize the Amex benefits because I find them too cumbersome to keep track of. i surely could get more value from Amex, but simply don't.

For earning, I use the Amex Blue for Biz, the Gold card for groceries, the Ink Unlimited and the Ink x5 at office supply and for cell phones. My Amex spend is mostly 2x or more, and my UR spend is mostly 1.5 or more. By pairing high earn daily use cards with the high end card redemptions, I can keep a steady stream of transferable points coming into the coffers. I'm finding less and less incentive to use cobranded cards of any sort, except for hitting targeted spend bonuses such as free hotel nights. Many of my cobranded airline and hotel cards have been downgraded to fee free cards and only get very occasional usage.