[mikeklaas]

Your question is relatively meaningless, since 'bytecode' covers such a wide gamut of possibilities.

Python's bytecode is very high-level and basically just saves the expense of parsing the code. The interpreter is not JIT-ed and thus very slow (compared to machine code).

Java's bytecode is much less dynamic. 'a + b' can execute arbitrary code in python, but in java it is known at compile-time whether it is addition between native types or string concat. Java has a very good JIT compiler and thus can be as fast as 1.5x the speed of c.