Here's a data point.

I just went to book a Marriott room using points over a very busy (and expensive!) holiday weekend in NYC. Hit Search and all the Marriott properties show up and all have very expensive rates. "Thank goodness I'm using points for this," I think to myself. I had forgotten to check that box in the search and do it again.

Now the search yields ZERO properties in Manhattan and my points that popular weekend are only good in Fairfields and Courtyards outside of Manhattan.

At least with SPG, if they have room for sale, they have a room for sale, be it for cash or points (or both). Why have all these rewards points from Marriott when I can't use them when it's most critical (for personal and expensive travel)?

I'm Gold with Marriott; Plat with SPG. Marriott just confirmed my 2014 choice of keep those chains in that order of priority for me.