I like the WP-100. It gets my teeth squeaky clean. I like the larger reservoir, so I don't have to keep refilling while cleaning my teeth. I also like the variable strength adjustment. Sometimes I need to crank it up to get a spot that has plaque building up.
The Waterpik opened my eyes to a new way to dental hygiene. I never knew just brushing my teeth left so many harmful food particles in my mouth. Easy to use and I feel confident I am cleaning my teeth properly.