Wink stones are cheaper because they are not coated, but they look just as realistic imo. The benefit to Asha is that the coating helps keep oils off the stone, so it stays cleaner longer, looking sparkly longer. I have not compared a Wink stone beside an Asha of the same size and cut, so the subtle differences, i am not sure about, but you can't really go wrong either way. Both stones will have a great cut and will be believable.
Joseph Schubach Jewelers