If your goal is just pure free nights, it's hard to beat Hyatt or SPG when they have a good promo going. Marriott's promos are almost always lackluster.

Part of it depends on your travel pattern though. I do a lot of 1 or 2 night stays, so when there is a stay based promo at SPG, you clean up. every 3 stays = free night at up to a cat 6 resort means that per week you could be earning the equivalent of like 50k marriott points ( I forgot the actual #).

On top of that, Marriott's are almost all the same and boring until you get into their much nicer hotels. Give me a Westin or Sheraton over a typical courtyard any day.

Do some searching as this thread has been beaten around a lot.

You are also making an unfair comparison because you're looking at your 50% bonus from marriott PLT, but you get the same 50% with SPG Gold. That said, Marriott does allow you to really generate points the quickest by just pure nights. The real key is maximizing promos. That's where SPG (and Hyatt) win out big time.

Finally, hotels tend to care that you're platinum - Marriott they don't really do anything for you from my experiences.