"In emerging markets, the iPhone 4S will continue to be the volume driver at the low end as the lack of subsidy in most markets leaves the iPhone 5c too highly priced to help drive further penetration," Gartner said.
The situation in mature markets such as the US and Europe is different, the firm said. A contract-free and unlocked 16GB version of the iPhone 5c is available for $549 (about Rs 34,700) in the US, while an unlocked and contract-free iPhone 5s can be bought for $649 (about Rs 41,000).
"Gartner believes the price difference between the iPhone 5c and 5s is not enough in mature markets, where prices are skewed by operator subsidies, to drive users away from the top of the line model," it added.
Apple did not immediately reply to an email seeking comment on the issue.
The new models helped Apple register a 23.2 per cent year-on-year jump in sales to 30.3 million units in the July-September quarter. However, the positive impact of these new models could have been greater had they not started shipping late in the quarter, Gartner said.
The firm added that there has been some inventory built up for the iPhone 5c, whereas the demand for 5s has been good leading to its stocks being sold out in many markets.
Earlier this month, billionaire Anil Ambani-promoted Reliance Communications tied-up with select credit card providers to offer the new iPhones at zero upfront cost. RCom will not charge customers any usage bill for 24 months under this offer.