You have FAR more control over the flow than with a siphon line. You can regulate flow at the spigot so you don't fill bottles too quickly. fast filling with some wands does froth up the beer, which means you aerated it, which means it may become oxidized.
frankly I just find it a lot easier. No racking cane to slide around, and since you just racked it to the bottling bucket, there is NO TRUB in the bottom, so you don't have to worry about your racking cane sliding around and sucking up a bunch of yeast, from primary or secondary.