The Loose Rings make the bit less fixed in the mouth which encourages mouthing and acceptance of the bit, while retaining the turning advantages of the full cheek.
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 maximize the effect.