It's very difficult to do a comparison like this in practice, because switching languages inherently involves a rewrite of a platform.
It has probably got more to do with the rewrite and the new architecture than whatever language it was written in.
Ruby binary trees: 57 seconds Scala binary trees: 11 seconds
[1] - http://benchmarksgame.alioth.debian.org/u64q/ruby.html [2] - http://benchmarksgame.alioth.debian.org/u64q/scala.html