Well, the thing is, at least as much as (and maybe more than?) Marriott, some of the Hilton brands are more consistent than others. IMHO you really have to check a DoubleTree, especially, on an individual basis, because the best ones can be nice but the worst ones will make you dream of staying at Hampton Inn (technically the lowest tier).

Sorry, I don't know the full rankding, but can do a little comparison: Hampton Inn is in the same category as Fairfield Inn (free breakfast and free internet for everyone regardless of status). Hilton Garden Inn is next step up probably, but Courtyard isn't a perfect comparison, because Hilton Garden Inn has a great breakfast which typically includes cooked-to-order eggs which is always free to HHonors Gold and Diamond, while Courtyard's breakfast is never free to Marriott elites no matter how elite no matter what day of the week (and may not be the same at any rate; I've never stayed at a Courtyard so I'm not familiar with what exactly the "Bistro" breakfast is). Homewood Suites is sort of like Springhill Siutes (or is Residence Inn closer?). Marriott is sort of like Hilton.

Plus be aware that the relationship between in-hotel benefits and elite level is more consistent in HHonors. You don't have to avoid one brand because you don't get elite perks there (like CY at Marriott). You don't have to think "what day of the week is this" because Hilton doesn't change elite benefits depending on day of the week (as Marriott does).