If you are allowed to write e.g., a Java program and run it on the JVM, the speedup will typically be on the orders of magnitude in favor of the JVM. Static type systems and extensive optimization matter.
However, chances are you have an Erlang program, and it's quite large. In this case, the speedup compared to the older bytecode interpreter is good for many programs. It is performance you get "for free" by upgrading.
The underlying reason for picking something like Erlang is robustness. Java isn't really built for this kind of programming, and the JVM doesn't directly facilitate it either.
However, chances are you have an Erlang program, and it's quite large. In this case, the speedup compared to the older bytecode interpreter is good for many programs. It is performance you get "for free" by upgrading.
The underlying reason for picking something like Erlang is robustness. Java isn't really built for this kind of programming, and the JVM doesn't directly facilitate it either.