FYI: If you are new to Scala, it is important to understand there is a large difference between wanting to write “scripts” with Scala, and fundamentally learning Scala itself.
THIS IS JUST MY PERSONAL OPINION:
With most scripting languages, the focus is on letting “non-software-engineers” (like Admins and DevOps) get things done. This means the scripting languages aren’t very principled and involve lots of “boilerplate” and “hacking” which “keeps things simpler”. Of course, scripts grow over time and eventually become un-simple. And that’s when all the headaches of that scripting language get magnified into unmanageable and unmaintainable complexity.
Scala has almost exactly the opposite design goals. This means “scripting” is NOT an ideal approach to learning Scala itself. However, it IS an ideal approach to taming the complexity inherent in other scripting languages.
If you are learning Scala, then definitely head in the Ammonite direction as Li does a fantastic job guiding you through all sorts of “scripting” priority things.
However, if you already know Scala and you are attempting to write things that fall along the more principled FP direction, then Scala-CLI is likely a better choice.
Again, this is an OPINION. So, be sure to value it exactly how much it cost you. 