[on_and_off]

I have starting learning kotlin 2 years ago for Android but I have not yet touched Scala, so I am also biased.

After 2 hours with the kotlin koans (short exercises allowing you to learn the language), it was already clear that Kotlin solves most of java's limitations when writing android apps.

higher order functions : so powerful .. at the cost of dex (and I don't really care about dex size), I can get very flexible calls.

nullability backed in the compiler

100 % java interop

data classes

default parameters values ..

etc

IIRC, the larger runtime was what prevented Scala from being interesting on Android. I know that Scaloid has been working on making it more svelte though.