The Waterpik Aquarius WP-660 excels for pure water flossing with its 22 oz reservoir and 90-second runtime per fill versus the Sonic Fusion 2.0's 10 oz and 45 seconds. The Sonic Fusion 2.0 provides unique 2-in-1 sonic brushing plus flossing but requires more frequent refills. Consumer Reports and dental association reviews note both reduce plaque effectively when used daily but the Aquarius is ...