You do realize that until recently moving Java to 64 bit meant a 10% or bigger performance penalty, and that the fixes for this are mostly just tricks that make the internals of the 64bit version play with memory so that it stores the memory pointers as 32 bits (to get around having to move 64bit pointers around).
The performance increase is probably not about 64bit (and you might not be running in 64bit mode), but about optimizations in the frameworks.
I don't understand this obsession people have with 64bit computing... bigger numbers do not make things automatically better.