It's tough to know if you got the cheapest hotel rate. A lot of that has to do with timing. Published hotel rates, like airfares, fluctuate. Availability changes based on occupancy. Corporate rates aren't always as accessible as many program managers would like.
Some big chains also are more actively favoring direct bookers. They offer various enticements, notably free Wi-Fi. Loyalty program members booking directly with Starwood and Hilton get discounted rates. It seems like . . .