It seems to depend on the ripeness of the olive. Green olives remain firm and “toothsome”, with the firmness decreasing as the olives turn dark. This year, we have cured olives from NoCal Central Valley and from our own in the Sierra foothills. The difference was that the valley olives were picked a month or more earlier than ours and were also larger.
In the past, we have experimented with salt cure, water cure and brine cure. Finally, the lye cure gives us the best results. It’s all a matter of taste. (I shared some salt cure with a Turkish neighbor who said that they took him home; he was overjoyed. We thought they were close to inedible. Go figure.)