The DiamondClean 9000 outperforms the ProtectiveClean 6100 in plaque removal (30% higher per Consumer Reports) and offers extensive coaching via its Bluetooth app (CNET), but it costs significantly more (Wirecutter). For users who prioritize premium features and personalized feedback, the DiamondClean is the clear winner, while the ProtectiveClean delivers solid cleaning at a budget‑friendly pr...