Don't get me wrong, since using Clojure and Scala quite a lot over the last month, I very much like both languages. If I were to do a very large project from scratch, I would likely choose Scala (love the concise syntax). Clojure's interop with Java is great and Clojure is a nice language to code in. Both languages have helpful communities behind them.

All that said, I saw two things this morning that convinced me that JRuby has a real advantage because it combines the rich Java and Rails infrastructures. These two cool things were:
  • Using Datamapper with two different back end stores (MySQL and MongoDB) - architectually pleasing!
  • The Neo4j + Lucene JRuby wrapper that provides a very "Ruby like" interface for the Neo4j graph database with seemless indexing/search support using Lucene (I just did something similar wrapping Lucene and Sesame (RDF data store)).