Like I said before there are many different manufacturers making many different units all using the same membranes. So as far as there ability to make purified water all of the RO systems on the market today will do that. Some of the RO’s will use more water to accomplish this that other units. I would say that efficiency is probably the biggest difference. The most efficient RO on the market today from any manufacturer would be the water captive type. This type of unit has been around for quite some time but you will rarely see them because they are problematic. I have heard that Kinetico has begun marketing a water captive system. This system uses the tap pressure to dispense the stored water inside the tank. This eliminates back pressure and allows the most amount of the net pressure into the concentrate side of the membrane. A good runner up to a water captive system would be an air captive unit (like the ones we have all seen) equipped with a permeate pump. If you would like any additional information on the multitude of RO systems on the market please contact me personally. I have over 15 years expirience with residential and comercial RO systems.