As Marriott Life Time Platinum I got my self as well SPG Platinum. Recently I've decided to try SPG that was on slightly better location than Marriott hotel ( prices completely the same ), and just let me see if I got it correctly regarding points earned for my stay.
What Marriott/SPG Rewards program give's you on, let's say, 1000$ worth of stay :
Marriott: 1.000$ x10 ( 10 points per $ spent ) + 50% for Platinum = 15,000 points
SPG: 1.000$ x 3 ( Platinum: 3 points per $ spent ) = 3,000 points x 3 ( conversion to Marriott ) = 9,000 points
In 14 days it wont matter anymore as it will be all one program, but based on this I just lost 6,000 points, which is like 40%
Yep, I know, I should get informed my self little better before...