Ask HN: Scala or Ruby?

We're about to develop a Big Data product. We're very comfortable on Ruby and Java. However, there is an uprising popularity on Scala w.r.t Big Data (i.e. Apache Spark, PredictionIO etc). Since there will be many sub-systems like UX, Business Logic etc. down to the Big Data part, we're considering Ruby will be OK for those parts where we can switch to Java for Big Data crunching. However, I'd like to verify this choice w.r.t Scala-only stack (using Spray, Akka etc. for other subsystems than Big Data part).