In the wake of the most recent round of quarterly earnings reports, there’s been quite a bit of discussion over just who the leader of the pack is when it comes to the smartphone market. While Samsung passed Nokia to become the world’s biggest overall cell phone vendor, two conflicting analyses led to some uncertainty as to whether they had also passed Apple to become the top smartphone maker. Another report seemed to confirm that yes, Samsung is the world’s leading smartphone maker.

While those reports were based on unit sales, a study released today by Wireless Intelligence paints a slightly different story. Drawing information from the quarterly reports of the U.S.’s top wireless carriers – AT&T, Verizon, and Sprint – Wireless Intelligence found that the iPhone is America’s top-selling smartphone by a margin of nearly two-to-one.

During the first quarter of 2012, AT&T reported that 4.3 million of their 5.5 million smartphone activations (78%) were iPhones. Meanwhile 3.2 million (51%) of Verizon’s smartphone activations were iPhones, and 1.5 million (60%) of Sprint’s smartphone activations were iPhones. All told, then, the iPhone accounted for 9 million of the roughly 13.5 million smartphones sold by the three companies.

Wireless Intelligence’s data lines up with a report published yesterday by Business Insider, which showed that that the iPhone was beating Google’s Android platform in the U.S. smartphone market. Based on the same sales data used by Wireless Intelligence, BI concludes that the iPhone has 63% of the smartphone market among the big three carriers. These carriers, in turn, account for about 80% of the overal U.S. mobile phone market. Consequently, the iPhone accounts for 50% of the U.S. smartphone market in the first quarter.

That, however, is contrary to a report released by NPD Group yesterday. This report showed Apple with a mere 29% of the smartphone market, while Android reportedly had 61%. While BI and Wireless Intelligence are using carrier sales data, NPD’s data comes from a survey of 12,811 consumers. NPD responded to BI’s report by pointing out that they track “sellthrough of new handsets,” rather than activations, that they only track consumer sales, not enterprise sales, and that the big three carriers actually only account for 60% of the U.S. mobile phone market.

All in all, NPD’s reasoning seems a bit problematic. While they have a point about activations being different than new sales, it’s unlikely that the difference between the two is great enough to account for the discrepancy between the two sets of numbers.