I haven't used the latest Oregon chain, but I've run a fair amount of carlton, oregon and stihl.
I can tell you that for square ground which I usually run, I vastly prefer the Stihl. It defintely holds a square edge much better, and I think it is a better quality chain in general. Since I use a grinder I don't care that it is harder, and I can buy it as cheap as Oregon or Carlton, so the last several reels I've bought (and probably all future chain) will be Stihl.
If I had to buy Stihl chain by the loop and at standard Stihl dealer's prices then maybe I would rethink that, but I don't.
I read alot about reduced vibration in chains, but mostly I am confused by it. In my experience a sharp square RSLK (and depth gauges within spec and not too low) and the power to pull it make the smoothest cut in the hand. The tougher the wood, the more the importance of sharpness for smoothness-the goal is to cleanly sever wood fibers..