E*Trade customers are now eligible to sign up for the American Express Platinum card from Morgan Stanley, per this landing page.
This makes it super easy for anyone to have that version of the AmEx Platinum card with a free E*Trade brokerage account.
The big advantage of the Morgan Stanley flavor of American Express Platinum that the first authorized user Platinum card is free and gets the lounge benefits at no additional cost. The other things people mention is that sometimes it’s easier to get approved for the MS Platinum, and the card also allows 1 cent-per-point cashout of Membership Rewards points.
Hat tip to reader Alex

