After searching the web for “spring vs jee” (because I have been wondering what to learn), I conclude that this is a neverending debate, both are solid choices nowadays, many people still favor one or the other, and that both options are not completely mutually exclusive. So, while there is no definite recommendation for Java development, I wonder whether there is one for Kotlin development. After all, Spring has added official Kotlin support, but I cannot assess how big of a deal that is. Any Kotlin-specific opinions?
I would recommend Spring. Take a look at Spring Kotlin Support.
A little example helps to understand the benefits of dedicated Kotlin support: You can use nullable types and default values in Spring’s web frameworks, while you have to use the old annotation based approach with Java EE (JAX-RS in this case).