Advantage is that it puts weight on feeder calves and is good for stocker cattle that are either backgrounded or being fattened up for the slaughter plant. Also it's like candy to them, if they're not fed it too often that they get picky.
Disadvantages are labour and time, as well as storing and making the silage the right way so's it don't spoil. And also having the right forages to make GOOD silage, like barley or corn.
Me and my folks have done silaging for the past few years, and it's a great, if not better alternative than feeding hay all through the winter. We make our own silage, with two-row Ponoka variety barley, common up where we are.