Tiny Cooling Fan How to identify the amount of good or bad?

Do you know how to identify the quality of "Tiny Cooling Fan" is good or bad it? Today around this problem, small as you simply explain. I believe that many buyers and cooling fan cooling fan manufacturers are aware of, "Tiny Cooling Fan" oil-bearing and ball, that first of all we start to identify the bearing, oil prices lower bearing turn voice is small, some manufacturers providers within the oil-bearing plus Teflon, making the fan also has a ball bearing reliability, and then sell high. Ball bearing "Tiny Cooling Fan" oil-bearing noise ratio, the price is relatively more expensive, but more reliable, universal life longer than the oil bearing.