Yet online travel agencies are still fierce competitors. Although a head-to-head matchup favors suppliers, many consumers still say "It depends" when it comes to their purchase preferences, according to a survey conducted by market research firm eVOC Insights and RelevantView.

eMarketer senior analyst and travel specialist Jeffrey Grau thinks the "It depends" crowd has good reasons for using both online travel agencies (OTAs) and suppliers.

"For many people, it's not a black-and-white choice. Each channel has a different set of attributes. The agencies give you a broad selection, and make it easy to book multiple travel segments at the same time, such as hotels, airlines and car rentals. For details about a lodging facility, however, the supplier wins out. More importantly, supplier loyalty program points are easier to get directly from the supplier," said Mr. Grau

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