It is my opinion that nothing beats traditional brushing and flossing. Mechanical removal of plaque and food debris in the space between the root and the gum flap is key to controlling inflamation caused by bacteria in that space. The Waterpik cannot project a strong enough jet to get into that space to clean it out.
By leaning the floss against the root of the teeth and rubbing that root with the floss we can remove plaque much more effectively in the gum pocket.