Some may disagree, but other than the 48 hour guaranteed room and the plat arrival gift (I always take the 500 points), I don't see much out of platinum that is better than gold. Gold gets concierge lounge access, guaranteed room type, and EEO's. Plat gets their own phone line, not sure if it's thats anything to care about.

One unwritten benefit that has been referenced on Flyertalk is the soft landing from platinum to gold - if you make plat status for 2010 and don't stay enough nights in 2010 for gold status in 2011, the soft landing means you would be gold regardless. That might be a good reason to get platinum this year if you can (though it's an unofficial benefit, so Marriott can do whatever they please with the soft landings in the future). If you know you are doing 55+ nights next year then the 20 rollover nights is nothing to frown at.

Also, marriott uses the rolling year to do status qualifications as well, so if you have stays planned early next year and your 70 night were towards the end of this year, you could get platinum status midway through 2010 if at any point you have 75 nights or more in a year's time. You would then get plat status through the end of 2011, and probably gold through the end of 2012.