I don't think they're that similar? I dislike C++ because of its large amount of unsafe constructs and huge number of special-cased language-level features; I like Scala because it's the most practical language I've found for writing safe enough code and because the core language is quite small, with many features moved out into libraries or patterns of combining simpler features.

They are both multi-paradigm languages with plenty of modes of expression. Both provide sufficient ways to hurt yourself. There are enough Scala implementation warts to trap the unwary.

edit - in my parent comment I should have restricted scope of the comment to the use of the language for this purpose.

Scala is different in that it has stronger type system, automatic memory management, the language is well-specified and is based on JVM, a reliable runtime. I would suggest that even Java would be much better choice than C++ for that project.