While I'm not familiar with those properties myself, Doubletree is the least "standardized" of all Hilton brands, so they can be anywhere from near-Hilton "quality" to somewhat dated and shabby (see also: IHG's Holiday Inn brand). HGI, on the other hand, is quite standardized, with most properties being well furnished and up-to-date looking.

You do not say in your profile whether you have any status with Hilton. The point costs are loaded as the default values for those chains, while the cash price reflects what the owners think they can get for that night. In this case, hear the faintest of warning bells that this DT may not be one of the more ... impressive properties of their brand.