Old style signs next to Snapchat, Facebook and Twitter signs. Getty Images

Twitter and Snap are more attractive now that Facebook is no longer the "only game in town" for advertisers, GBH Insights said Wednesday. "We believe there are a confluence of factors that have catalyzed the growth prospects of both Twitter and Snapchat in the near-term, with some of this momentum clearly happening at the expense of the Facebook platform," Daniel Ives, head of technology research at GBH, said in a note. Ives estimates that, after only advertising on Facebook, 15 percent to 20 percent of traditional social media advertisers are experimenting with Twitter ads. That should add about 1.5 percent to 2 percent of additional advertising growth, he said.

The technology analyst also said some advertisers are looking more closely at Snapchat. And despite the negative reviews of the app redesign that prompted Citi on Tuesday to downgrade the stock to sell, Ives said Snapchat's app redesign is beneficial in the long term. He predicts it will bring new users, especially those in the key advertising target market of the older age category. Twitter share prices were little changed, while Snap shares fell 2 percent. Facebook shares climbed 2.4 percent. "We do believe a renaissance of growth and new [monthly active user]/engagement is starting to benefit both SNAP and Twitter as organic initiatives/targeted ad algorithms, app redesign, and a host of content driven campaigns are serving as positive catalysts in the field for 2018," Ives said. Over the last six months, shares of Mark Zuckerberg's company have struggled relative to the two other social media stocks. Facebook shares climbed just 5 percent over the last half year through Tuesday's close. In contrast, Twitter shares are up 105 percent while Snap shares are up 35 percent. Facebook said on Jan. 31 that fourth-quarter updates to video recommendations contributed to a 5 percent drop in time users spent on the social media network. The company has announced other changes to its news feed recently to emphasize posts from personal connections rather than brands. Twitter and Snapchat parent Snap posted more upbeat quarterly reports earlier this month. Twitter reported net profit for the first time ever, while Snap posted a smaller-than-expected loss per share amid a sharp double-digit jump in revenue.