You can but I don't think that's a particularly fair, representative or insightful comment on why the difference exists.
The developers of MRI are focused on developing an interesting and useful language first and everything else second.
The developers of JRuby are focused on replicating that language on the JVM. They benefit from a sophisticated JIT and GC and in later JVMs some direct help, none of which diminishes their own efforts to improve performance.
Sure you can write slow code in anything but I don't see how that's in any way related to 'your JRuby/CRuby' comparison.
By that logic, any mention of any difference between any language, runtime or its implementation can simply be dismissed by 'well, they ARE all Turing equivalent!'
I just wanted to point out on your previous comment - it is not surprise that only choosing some particular language doesn't mean a guaranteed performance.
The developers of MRI are focused on developing an interesting and useful language first and everything else second. The developers of JRuby are focused on replicating that language on the JVM. They benefit from a sophisticated JIT and GC and in later JVMs some direct help, none of which diminishes their own efforts to improve performance.
Sure you can write slow code in anything but I don't see how that's in any way related to 'your JRuby/CRuby' comparison.
By that logic, any mention of any difference between any language, runtime or its implementation can simply be dismissed by 'well, they ARE all Turing equivalent!'