I used to do copper when I first got in to the hobby and rushed everything and had a bunch of sick fish. Then I tried hypo a few months ago when I had one sick fish, which is supposed to be much easier on the fish. I treated all fish in the tank immediately - do not waste time thinking you don't need to treat them all, I have made this mistake. None of the other fish ever got it and they first fish recovered within a couple of days and never showed white spot since.
In my experience hypo results in much less stress on the fish if caught early, ich will literally fall off the fish overnight, although you must keep them in hypo for several weeks to make sure the parasites die. The fish get healthy quickly with less stress (most fish do fine in 1.010 SG), which results in lower mortality rates.