Dont think there is a page that describes the differences

Best thing to do is download and install Mach3 and mess around with it without setting it up to run your mill. That way you can see what it looks like and it will giove you an idea of the differences. You can have Mach2 and Mach3 on the same computer and they wont interfere with each other, only thing you cant do is have both open at the same time.
Hood