Kotlin did pretty well in the matrix [1], though it appeared to be weaker in the areas of memory control and thread safety. These two areas stood out as important because we were bit by them over and over when we had two parallel native codebases written in Java + Objective C.
Not crashing our customer applications, and not exposing them to any additional security vulnerabilities is top priority.
It's important to keep in mind that we evaluated these options 18 months ago (roughly), so numbers might have changed.
Note that we specifically do not use Swift at this time -- even in our platform glue -- because we cannot guarantee that a Swift runtime appears on all devices that we are targeting. We are evaluating options to allow us to use Swift in our glue.
Not crashing our customer applications, and not exposing them to any additional security vulnerabilities is top priority.
It's important to keep in mind that we evaluated these options 18 months ago (roughly), so numbers might have changed.
Note that we specifically do not use Swift at this time -- even in our platform glue -- because we cannot guarantee that a Swift runtime appears on all devices that we are targeting. We are evaluating options to allow us to use Swift in our glue.
[1] https://language-compare.glitch.me/