It depends what you're using it for. If you want to old school mid to late 00s twitter that was just random anonymous people microblogging random thoughts and sharing links and pics then you'll be happy to be back home.

If you followed twitter because it was a way to get direct contact and access to industry professionals, celebrities, reporters, breaking news, specific niche communities that just dont exist or barely do on mastodon, then you will be unhappy with it. Mastodon will get you uh, George Takei, Zach Weiner, and the technologyconnections guy.

For example of the difference and why many people just dont care for jumping into mastodon I'll use My wrestling feed as an example. On mastodon it is mostly one guy who's enthusiastic about womens wrestling(seriously if he stopped my feed would die), one news reposting site(which honestly isnt a bad thing cause wrestling news is awful), and a handful of other people. Twitter has lots of memes and clips from the fans after episodes air, lots of links to primary sources and news sites, and the actual wrestlers interacting cutting kayfabe online promos, promoting themselves, and interacting with fans.

This applies to a number of niches, hobbies, and fan interests on twitter. Bigger isnt necessarily better but the size and adoption of twitter is a huge strength.