The pro's to a auto blowdown is that it will happen at the set time every day, just set it and forget it.
The con's to a auto blowdown is that you have to make sure the drain pipe is cleaned of lime periodically to ensure it is being blowdown since no one visibly see's the blowdown daily.
The pro's to a manual blowdown is that someone has to see the boiler every day and can do a once over to make sure things are in good working order.
The con's to a manual blowdown is that the blowdown (whether manual or auto) is quite violent and takes extreme caution.
View a video of the blowdown here Generator Blowdown
It would be piped to a drain, tub, or sink, not a bucket as in this example.