Scala is much faster. I work with both of these languages, and I like them both, but when run time speed matters, I go straight to Scala.

Benchmarks bear me out on this. Python 3 vs Scala. Scala averages out to being about 25 times faster. It's 64 times faster on one of these benchmarks.

A few months ago, I had an experience in which I replaced slow running Python code with a Scala program that ran 215 times faster. It was a program interfacing to an Oracle database and the "extra" difference is attributable to how blazing fast the Oracle JDBC driver is in comparison to Python's cx_Oracle driver. A 25 minute task dropped to seven seconds.