Marriott definitely treats their Platinums better. It really isn't close. Think of SGP Platinum as Marriott Silver except with a few more perks.

That said, I love SPG because of using points for stays and because when I take the wife out on a leisure trip we're at a cool W hotel, not a business-ie Marriott.

Marriott is weak on aggressive rate specials, but Marriott destroys anything SPG does on points and free stay promos.

I feel SPG is slightly cooler, and Marriott is just for expense report people.