It is not very likely that one would be quieter than the other, it is possible, but in general if the noise persists, the best bet is going to be sending the pump in. More often the cause is that the well the impeller sits in is not perfectly straight, up until 2006 this was completely done by hand so they could have a slight angle, the only fix then is hand fitting parts and minor adjustments. On the earlier pumps, the plastic castings were assembled, the coil and circuitry soldered and installed, placed in a wood jig, the polyurethane potting was hand poured and they cured for a week. After 2006 this was automated to some extent and a more sophisticated curing frame was used to prevent any misalignment. However, they will absolutely be quieter than they are now in a couple weeks and we will do our best, but if they aren't quiet enough, best bet is send in the pump.