it depend on what you are going to do. if you are
doing something on your computer & go to the restroom
or get ready to eat & you come back then you might
want to do screensaver, but if you use your computer
& you find out that you have to go to pick up
your Grandmother from the airport, but you are coming back
home, then you use the standby option.
so if you leave your computer for a few minutes, use the
screensaver mode & if you are gone for an hour or so, then
you use the standby mode.