Since the competing rate is just $20 lower than on Hilton.com, I think that's a small enough difference that it's worth the risk. I mean, even if you're staying 5 nights, you'd only pay $100 more for booking through Hilton. Just examine that hotels.com rate METICULOUSLY, making sure every single detail is the same. Be sure to go beyond the initial rate listings--you need to get to the page where you're filling in your name so that you can be sure the rate actually goes through. Screencap everything.