Computer Language Benchmarks Game:
Speed test java/scala 1.71/2.25
Memory test java/scala 66.55/80.81
So, this benchmarks say that java is 24% faster and scala uses 21% more memory.
All-in-all it's no big deal and should not matter in real world apps, where most of the time is consumed by database and network.
Bottom line: If Scala makes you and your team (and people taking project over when you leave) more productive, then you should go for it.
