A wordpress hosting service does one thing, maintain WP. They live and breath it. They apply important updates right away. They are more secure than my WP would be, since I don't live and breath it. And, if I'm using a WP hosting service and they get owned, no skin off my nose. I have daily backups of my WP site, so I can move to another one that is more secure, should my current hosting service prove unreliable.