Snap's (NYSE:SNAP) Snapchat is the most popular social network for U.S. teens, according to eMarketer. Snapchat has 16.4 million teen users in America, compared to 12.8 million on Facebook's (NASDAQ:FB) Instagram. However, another recent eMarketer survey found that companies overwhelmingly prefer Instagram to Snapchat for marketing purposes.

Graph showing percentage of marketers who use Snapchat and Instagram.

Data source: eMarketer. Chart by author.

That's likely because Instagram has more overall users than Snapchat. Instagram has over a billion monthly active users and over 400 million daily active users on Instagram Stories. Snapchat finished last quarter with just 186 million daily active users.

Another major reason Snapchat likely lags Instagram is because it's a paid advertising platform. Instagram, however, encourages brands to post photos, videos, and stories for free, which lets them organically grow their social media followings without purchasing ads. Instagram's connection to Facebook also lets marketers simultaneously buy ads on both platforms, reaching a much larger audience than Snapchat. Teens also have less purchasing power than older users, which could limit the appeal of Snapchat's ads.

This report isn't all bad news for Snapchat, since its share is still growing. But it indicates that Snapchat could remain in Instagram's shadow for the foreseeable future.

Leo Sun owns shares of Facebook. The Motley Fool owns shares of and recommends Facebook. The Motley Fool has a disclosure policy.