Thanks! I also saw this from apple support section, (which answers my own question.LOL, but can be a good reference for everyone)
"The main advantage is that you can address vast amounts of memory. With 64-bit mode, the application memory is not limited to 4GB as with 32-bit applications, so there is essentially no practical limit by today's standards. As a result, all the installed memory that is not needed by the OS is available for use by Logic Pro or MainStage and all the included plug-ins, which can be meaningful if your Mac has more than 4GB of memory installed."