Based on early returns, Apple's flagship iPhone 5s is selling twice as fast the cheaper iPhone 5c.

According to a new analysis from the Consumer Intelligence Research Partners, which surveyed consumers who bought the latest iPhones in late September, the 5s accounted for 64 percent of total iPhone sales, with the mid-tier 5c accounting for 27 percent and the legacy iPhone 4s taking up the remaining 9 percent.

Observers believe that's because enthusiasts who tend to buy early are opting for the 5s. That may not last.

"The relative performance of all three iPhones is generally in line with the performance of the similarly priced phones following the launch of the iPhone 5 in 2012," CIRP co-founder Josh Lowitz told AllThingsD. "Over time, the lower-priced phones have tended to gain share versus the flagship phone, after the initial rush of dedicated upgraders to the newest device. So we expect that the 5c will account for a higher percent of total U.S. iPhone sales in the coming months, but the design changes may alter that dynamic. The iPhone 5c may appeal to different buyers than the legacy 4s did last year, or the new 5s will this year."

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