thanks...can you define heavier duty motor? and how do RMP's fact in? looking at the specs what are the key differences? x01 -Motor: 120V, 60 Hz, 2.5 A Single Speed: 5500 RPM (No Load) x02 -Motor: 120 V, 60 Hz, 2.8 A (3450 RPM) Single Speed: 6900 RPM