The main advantage of a hydro clutch IMO is the consistent performance and reduced maintenance. There is no cable to stretch, bind, adjust, or wear out. You can race all day with a hydro clutch and not ever have to adjust a cable.
BUT, outside of a racetrack, a hydro clutch really isn't necessary. Keep a cable properly-lubed and adjusted, and its good to go for years of use with just an occasional adjustment. And you can buy an easy-pull cable-operated clutch lever for maybe £15 that works nearly as well as a hydro setup for the casual rider.