As I understand it, currently all languages are compiled/run in debug mode. Compilers which have optimization options do not have them turned on.
But some languages have ways to turn some or all of those optimizations on in the source code itself. This can lead to massive performance differences. making those languages a clear best choice in contests where performance is a factor, even if you would rather use one of the others.
Solutions to this problem?
Optional release mode checkbox in the IDE so any language can be compiled with some reasonable release mode setting?
Disable optimization pragmas in languages that have them? This would still have the problem that some languages debug modes are much closer to release modes than others.