Can't think of any situation when you'd "need" an Amex card. If you lost your MC/Visa or had an account issue, another MC or Visa would be a better backup, IMHO.

Agree with the comments so far... either Amex Plat Chargecard so you can benefit from Priority Pass etc, or none of the chargecards.

Amex works out expensive when used abroad compared with Nationwide Visa etc.