Originally Posted by
Antarius
I believe you still need both apps if you plan on staying at Marriott and SPG properties for the short term. The only thing being combined now is the rewards program and not the reservation system. To your bolded point, this is correct only if you use the app for rewards balances. Check in, requests etc. still likely needs both.
Come 2019, then it should go down to 1.
You can now already book Rewards legacy and SPG legacy properties from either account. Try it. Pick any large city that has both legacies. You'll see both.
Until I combine my accounts, I will use my Marriott Rewards account to make reservations, even if I'm planning to stay at a Westin or Aloft.
Combining accounts will also mean being able to see all future reservation across both legacies with the surviving account — and to check-in with app for that account.