If you are gonna grow 10 plants then I dont care what kind of lights they are, 72W is nowhere close to enough. Not only is it not strong enough, but it wont be able to cover the area that 10 plants take up... you are gonna end up doing more damage to your plants than good. Just go with the HPS, the electrictical bill wont be THAT much higher... you won't get squat if you use 76w.