A Ring cheek piece introduces poll pressure as well creating leverage on the mouthpiece, the 2½ Ring version is the softest version of ring bit as the ½ ring softens the leverage on the mouthpiece and poll.
The Waterford bit has many smooth flexible bumps or bubbles, which spreads the pressure over many points making it a light mouthpiece. The greater flexibility discourages a horse from leaning on it.
The Waterford bit is a good choice for a horse that leans, it also promotes mouthing and salivation. The Waterford is usually worn ¼" - ½" longer than your traditional mouthpiece in order to curl around the lips and maximise the effect.