Key performance indicators include vibration frequency (typically 8,000 to 12,000 RPM) and waterproof ratings (IPX5 to IPX7), especially for devices used with serums or in bathrooms. Check the charging interface, where USB Type-C is now the industry standard for faster charging and user convenience. Additionally, evaluate the ergonomic design; a lightweight, 45-degree angled head provides better contact with facial contours, significantly improving the end-user experience and reducing return rates.