It's hard to compare Clojure and Scala. Scala is a multi-paradigm programming language with strong OOP support and functional support. It's arguably more verbose than Clojure but looks much more similar to Java.
Clojure is a Lisp. Lisp stands aside all other programming languages, first of all, because it supports syntactic abstraction (a.k.a. "code is data"). Hardcode addicts (I'm not one of them) say there are only two programming languages - Lisp and non-Lisp.
When we made the decision to switch to Clojure, several things affected it, in no particular order:
- we had some people who were already very proficient in Lisp
- we liked how expressive and compact it was
- Lisp is considered to possess immense expressive power (see http://www.paulgraham.com/lisp.html)
- we were enamoured by Cascalog (http://nathanmarz.com/blog/introducing-cascalog-a-clojure-ba...), and it's written in and for Clojure. This one payed off very well.
- Lisp has a reputation of being great at manipulating data: lists, graphs, etc.
As for libraries, both Clojure and Scala are JVM-based, and Clojure has a very good syntax for Java interop, so all Java libraries are available to us. But, of course, Clojure community also spits out libraries like crazy, for example, take a look at this marvel which we use in Drake for parsing: https://github.com/joshua-choi/fnparse.
Thanks for your feedback. I've been playing around with both languages, and was leaning towards scala since it seemed more likely i could use it professionally, even though i liked clojure a bit more, sortta like the lisp like syntax.