Just figured I'd share my experiences here.
I found Hotwire to have the cheapest rates. This makes sense because Hotwire doesn't publish the hotel name until you pay for it, you're taking a bit of risk, and the only reason you'd take that additional risk is for a lower price.
The hotel gets something extra from Hotwire too, they avoid diluting their brand while selling excess inventory.
It all has to do with price discrimination and selling for cheapskate rates to cheapskates, and "rich" rates to the rich, even for the same good.
After purchasing, I found the Hotwire rate for the hotel was about $20/night cheaper than the same hotel on Hotels.com or Priceline.com. I have no idea whether the inventory is "worse" on Hotwire than on Hotels.com or Priceline.
I did find that on Hotwire, choosing a room for 3 adults resulted in getting a room with one queen size bed, and a pullout couch, so I ended up paying $20 extra at the hotel for a room with two double beds. I'm not sure if paying a little extra for a room for 4 adults would've saved me this extra expense, this is the first time I booked a hotel with any of these online services.