Although I was never an elite in their program, I will say one thing about Hyatt: my company always had negotiated rates with them that were pretty favorable, and those rates always came with upgrades to a concierge floor whenever it was available. AFAIK, Hyatt was the only chain with which our company had corporate rates that actually had upgrade language built into them.

In practice, the STL Hyatt and the Tampa Hyatt generally DID follow through with rooms on the "Business Class" floor or a concierge floor. (Those were the only two Hyatts at which I did a lot of biz stays.)

Marriott, HH, and SPG eventually came through with upgrades when on corp rates, but the upgrades were tied to your status, not the rate itself.