One problem with consolidation is that these cards are pretty dissimilar and simplification means giving up optionality.

Amex has a collection of things that are just a little bit better than other cards:

• Purchase protection terms may be similar, but the claim experience is vastly superior with Amex
• Given the choice, I'd take Amex Premium Global Assist over VISA Global Customer Assistance Services (GCAS) any day. Amex has that process down for wiring you some cash via Western Union, calling your hotel to make sure you can still get into your room, and expediting a card for global delivery. GCAS reports are a mixed bag.
• Lounge access is a bit more expansive with the Platinum card
• Amex has a bunch of scattered marketing efforts that may eventually be useful (suites at sports venues, pop-up events, etc)
• FHR offers guaranteed 4pm checkout (as others have pointed out)

The trade-off with all of that is you get points that have an industry low floor value and are only really useful if you're playing the award flight game, and most importantly you're using a card that simply won't be accepted everywhere.

Chase gives you a great option with a card that will be accepted just about everywhere and will earn well in the key spend categories of dining and general travel.

You can run a Chase-only setup, but it would be very difficult to run an Amex-only setup. If you want to avail yourself of some of the nice things that Amex can offer, you have to play in at least one other sandbox.