Agree that Kotlin has slightly better interoperability and IDE support (but Ceylon is interoperable with Java too and has an Eclipse-based IDE).
But I like Ceylon more because:
* Union and intersection types.
* I find the type system cleaner and more elegant.
* It's an attempt to build a whole new platform with a new SDK. Kotlin is, in a way, just a syntax skin over the Java platform.
* Reified generics. Kotlin got rid of them.
* I personally find Ceylon's "String str" more readable than Kotlin's "str: String".
* Type-safe metaprogramming.
* Comprehensions (not 100% sure Kotlin doesn't have them).
* It's compilable to JS.
* Slightly more regular syntax, more readable generic declarations, better web documentation, currying, spread operator, etc.
But I like Ceylon more because:
* Union and intersection types.
* I find the type system cleaner and more elegant.
* It's an attempt to build a whole new platform with a new SDK. Kotlin is, in a way, just a syntax skin over the Java platform.
* Reified generics. Kotlin got rid of them.
* I personally find Ceylon's "String str" more readable than Kotlin's "str: String".
* Type-safe metaprogramming.
* Comprehensions (not 100% sure Kotlin doesn't have them).
* It's compilable to JS.
* Slightly more regular syntax, more readable generic declarations, better web documentation, currying, spread operator, etc.