@zfoxfire: The win_startscript just grabs the memory parameter from the server.properties file and executes the server.jar with this argument. But the main reason to run the bat instead of the server.jar directly is to have a console available (many people just double click on the server.jar, which causes the server to run in the background - only way to close it would be to kill the process in the task manager).
We want to keep the start scripts as basic as possible, it's really just to cover the basic behaviour. I'm sure some people won't be happy if the server sets up new services in Windows^^