Ehh, he's the best, but I wouldn't say "Far better" than McDonagh.
And the gap between Del Zotto and any others listed for LA makes it much closer than you're suggesting.
Dude, don't kid yourself. Doughty is far better than McDonagh. They're the same age but Doughty has already achieved so much more.
4 full seasons (316gp) vs 1 1/2 seasons in the NHL (122gp)
43G-162pts in 316gp (11G-42pts/avg) vs 8G-41pts in 122gp (5G-27pts/avg)
1x Norris Finalist/1x Stanley Cup Winner/1x Gold Medal Winner/1x WJC Gold vs Nothing
Doughty scores more goals, more assists, is more physical.. He is just a far superior two-way force. McDonagh certainly does not have 60pt potential like Doughty has already proven in his sophomore season. However, he is the type of guy who will be a horse defensively and likely top out as a 40pt defenseman in his best season -- and there's really no shame in that. In his prime he will be known as a top 10 defenseman, but the problem is Doughty has already proven he can be in talks as a top 3 defenseman leaguewide, and even #1. He has also proven he can be a #1 defenseman on a Stanley Cup winning team.
Defenseman who can absolutely control the game on both sides of the ice are extremely rare. This is what makes Doughty such a valuable defenseman.