Though Twitter is a favourite place for US President Donald Trump to reach his audience, it has lost out to Facebook as Wall Street firm Jefferies slashed its investment rating on Twitter to neutral from buy.
Jefferies also cut Twitter's price target by $4, from $20 to $16 a share.
"In social (media) we see a clear winner in FB (Facebook)," Thill was quoted as saying.
According to Thill, the price target could fall further, another four per cent.
Twitter's shares rose only up a little more than one per cent in 2017 while the Facebook stocks rose over 40 per cent.
Unlike Twitter, Facebook has had no trouble to grow its user base and make money from advertising in the second quarter (Q2).
In Q2, the micro-blogging site's revenue was down five per cent to $574 million. Also, its monthly active user base showed a stagnation.
In an effort to attract advertisers, Twitter collaborated with several media houses to broadcast programmes and sports events live. But even that has not paid off as Facebook offers a stronger digital video propositions.
"We will pay close attention to advertiser sentiment over coming months and effectiveness of live video," Thill noted.