Realistically, there likely isn't a huge difference in their NHL-readiness.
They're both excellent players, Doughty has a little more offensive talent, while Schenn is a bit more stay at home.
But wouldn't you say the better player at this point is more NHL ready?
Also to take into account, it's MUCH easier to bring an 18 year old defenseman along in LA than it is in Toronto, especially given that both these guys are highly touted. If Doughty struggles in LA, it won't be big news. If Schenn struggles in Toronto, he has to watch his back on the way home. That's just the way it is.
I've just been led to believe that Doughty has a good shot at making the Kings roster, while Schenn, if I'm not mistaken, isn't even being considered in Toronto this season.
Both would contend for top D man honours at the WJC if they play.