Currently with the Marriott and Ritz Carlton credit cards you earn 5 points per dollar on Marriott and Ritz stays.
After the merger we are now able to transfer 1 Starpoint to Marriott for 3 Marriott Rewards Points. So let's do the math on a Marriott/Ritz stay with your SPG card:
(2 points per dollar) x (3 Marriott Rewards points per 1 Starpoint) = 6 Marriott Points!
That gives you one extra point per dollar using the SPG Amex instead of a Ritz or Marriott card.
See how the little things can add up?
The SPG Amex also gives you a 5,000 point bonus when you transfer 20,000 points, earning you even more points per dollar. It's an all around great card for everyday spend, but now an even more lucrative card for hotel stays in the Marriott/SPG/Ritz family.