I think the answer is quite simple. You might start out with Kotlin and get familiar with it. But when you get thirsty for more, arrow is the logical next step.

I think the answer is quite simple. You might start out with Kotlin and get familiar with it. But when you get thirsty for more, arrow is the logical next step. Going for Scala would require learning a lot of new stuff and once or even rewrite your things. It's the same for Scala and Haskell, which is why Scala is sometimes called Haskellator - I still would start a project in Scala because I'm more familiar with it.