[alexgaribay]

Scala and Play is a very fun stack to work with for backend. It has a lot of modern technologies needed to create awesome applications. Scala is slowly becoming more popular among startups in SF and London. Scala is a very fun language and I have enjoyed transitioning from being a Java developer to a Scala developer and learning functional paradigms in Scala.

With my Scala promotion aside, each of the stacks you have listed have great employability. You'll need to ask yourself what kind of things you are wanting to learn while using these stacks:

1. Do you want to use a dynamic language? (Python, Ruby)

2. Do you want to use a statically-typed language? (C#, F#, Java, Scala)

3. Do you want to learn functional programming? (F#, Scala, Python, Ruby)

4. Do you want to work with big data and ML? (Python, Scala)

5. Do you want the highest chance of employability? (C#, Java)