Apple's (NASDAQ:AAPL) newest iPhones went on sale on Sept. 19, and for the second year in a row the company introduced two new versions of the handset. Both phones have significantly larger screens than the 3.5-inch and 4-inch screens Apple previously used. The iPhone 6 screen measures 4.7 inches, while the iPhone 6 Plus is a full-fledged "phablet" with a 5.5-inch screen.

The new iPhones were guaranteed to be popular, as many customers have clamored for bigger screens. Yet the exact breakdown of demand between the iPhone 6 and the iPhone 6 Plus is a trickier question. On the one hand, the popularity of smartphones with 5-inch and larger screens has taken off -- nearly half of buyers globally are looking for phablets, according to Accenture.

Both new iPhones have bigger screens than earlier models. Photo: Apple.

On the other hand, loyal iPhone users are accustomed to smaller screens. As a result, they might prefer a more modest step-up in screen size. So which version is likely to be the most popular?

Is it the iPhone 6 Plus?
Bloomberg and several other media outlets said the giant iPhone 6 Plus wins the popularity contest. Bloomberg cited noted tech analyst Gene Munster for that factoid.

Munster and his team surveyed nearly 400 people waiting in line to buy new iPhones at the Apple Stores in New York and at the Mall of America in Minnesota. Fifty-seven percent of them plannied to buy the iPhone 6 Plus. Since phablets tend to be more popular outside the U.S., it thus might seem like a slam dunk that the iPhone 6 Plus would sell better overall than the iPhone 6.

However, talking to people in line at the Apple Store is an unscientific sampling method. In fact, it's virtually certain to introduce sampling bias. Consider that there are three main ways for consumers to buy the new iPhones: 1) through Apple's online store; 2) at an Apple Store location; or 3) from a third party (such as an electronics retailer or a major wireless carrier).

Long wait times for online orders caused many iPhone 6 Plus buyers to wait in line at the Apple Store instead. Photo: The Motley Fool.

When pre-sales for the new Apple smartphones began on Sept. 12, wait times for the iPhone 6 Plus quickly escalated to three to four weeks. Wait times at most U.S. wireless carriers were even longer. By contrast, some iPhone 6 models still had no wait after a full day of pre-sales. The longest wait times for the iPhone 6 were seven to 10 days.

Thus, people could pre-order the iPhone 6 and have the device show up soon after becoming available in stores. Most would-be iPhone 6 Plus buyers had to choose between a three-to-four-week wait and lining up at the Apple Store. Guess who was more likely to show up and stand in line at the store?

A look at the numbers
Through the first few days of availability, there's a clear winner in terms of popularity -- and it's not the iPhone 6 Plus! Usage of the iPhone 6 has been five to seven times higher than that of the iPhone 6 Plus since the two new models went on sale, according to data collected by Fiksu.

To be fair, this number is biased in favor of the iPhone 6. Apple has had more trouble building the iPhone 6 Plus, causing greater shortages of that model.

The iPhone 6 is the fastest-selling iPhone ever, by a wide margin. Photo: Apple.

Still, uptake of the iPhone 6 has been more than twice as fast as that of any previous iPhone model. That's not very consistent with it being the less popular model. The "popularity gap" might shrink over time, but Apple's iPhone 6 is still likely to outsell the iPhone 6 Plus by at least 2:1 or 3:1 in the long run.

The iPhone 6 will be king
The iPhone 6 has a lot of advantages in going up against the iPhone 6 Plus for the sales crown. Most important, it's $100 cheaper. Considering that iPhone users have survived for years with much smaller screens, most buyers are likely to opt for the cheaper option, which still delivers a 38% increase in viewing area compared to the last two batches of iPhones.

The raft of news stories proclaiming the iPhone 6 Plus is "more popular" than the iPhone 6 have understandably caused a lot of confusion about which model is selling better. However, the smaller iPhone 6 has raced out to a big lead in terms of usage, and it is likely to maintain its spot as the best-selling iPhone throughout the next year.

Adam Levine-Weinberg is long January 2016 $80 calls on Apple. The Motley Fool recommends Apple. The Motley Fool owns shares of Apple. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.