DoubleTree by Hilton has been cornering the market on conversion brand hotels, nearly doubling its rooms since 2007. But Marriott International wants to change all that.

Marriott's North American chief development officer, Noah Silverman, believes the only reason DoubleTree has had so much success is because it doesn't have a competitor like Marriott.

Earlier this year, Marriott paid $135M for Canada-based Delta Hotels and Resorts, positioning it as a US conversion brand. Delta signed up its first US hotel in Orlando last month.

DoubleTree owes its success to convincing hotel owners of rival brands to switch flags. As of the end of September, 96% of its 4,406 new rooms added in the past 12 months were conversions. Hotel owners can save millions with DoubleTree because it has some freedom in its standards, like allowing individual air-conditioning units in rooms instead of requiring owners to install one central air system.

Silverman says Delta will allow similar flexibility, including stucco "cottage cheese" ceilings, bathtub showers, and in-wall air-conditioning systems. It'll also be up to 50% less to convert a hotel to Delta compared to upgrading to Marriott. [WSJ]