The 3M stuff is excellent, that's what I first used. My son had the Meguiars stuff and Senna has my bottle of 3M so I borrowed my son's.
I think what causes the etching is the chemicals in our water. Probably no way to prevent it. I can't suggest enough that you invest in a Porter Cable polisher.....your headlights will look better than new with that and one of the plastic polishes.
Pat