Threads is attempting to recreate #Birdsite but not fully functional. Because it's owned by #Meta, lots of official accounts, sports-related, and all of the news outlets are there.
Whereas Mastodon has a chill vibe with lots of smart, talented, serious people, wanting to spread good stuff, especially their hobbies, and good info about everything.
When Threads connects to the #Fediverse, the Fediverse will expand exponentially.