but isnt lanching batch from maya and closing it , the same thing?
well sortof, it does fragment your memory space tough. See programs are prefeerably interested in long sequences of continious memory. Since maya uses up a lot its a bad starting point. But fi you have lots of memory dont bother, after all you CAN use batch for bacground processing (for example if you make shading tests where you animate a aattribute so that you get a palette to choose from).
Launching batch form maya does however cause the file to be saved one more time.