Originally Posted by gleff
This is frustrating in a world where non-SPG website bookings aren't supposed to receive benefits, but often times a property will appear sold out on the SPG website but will be available elsewhere such as on Expedia. This could be because Expedia has inventory to resell, or because there's some sort of a delay in updating the different CRS' being used. Either way, it's often the case that you can pay full rack for a room on Expedia, not be able to get the room on SPG, and yet supposedly be denied benefits . . .
But if you must stay at a property, for reasons other than SPG status/benefits, always be sure to check a variety of booking engines and resellers.
I agree, you should definitely check 3rd party web sites. The individual hotels sell part of their inventory to 3rd parties such as Expedia. Sometimes you will only be able to book it through a third party and not through any other means.