Why would any serious team use flutter over React Native for their apps?

When it comes to my personal projects, I'd do what I want.

I find Flutter to be a much cleaner ecosystem then React Native. I tire of trying to sort out 800 different Babel versions, and fighting the JavaScript build chain.

For the projects I build, Flutter gets the job done much faster than react ever could. Having a real type system is worth it for me.

That said, you're phrasing this as someone looking for an argument. Different people like different things, for example, I think it's stupid to ever spend more than $30,000 on a car. Even if you need to buy something new, you can buy something extremely nice for 25k or so.

I don't go to car forums to argue with people about their lives though.

Your current question sort of invites some flamey style arguments. I think you are asking:

For people shipping production apps, Did you (and would you still) choose flutter or react native? Why?

I find it comedic that we have gotten to the point where people assume javascript is the only "professional" language for web development. I used to get put down for focusing on javascript/node when node was an early release.

Ask any mobile trading app and they will tell you how slow React Native is.