Butcher may have a better stat line, and is playing better than Bigras in this tournament, but they really can't be compared. Different styles develop differently and have different impacts at different ages. Offensive defensemen tend to have a large impact in juniors, but only a select few can have the same level impact as they move into the professional ranks.
Butcher is playing a very risky style in this tournament. Like SEPH said, he isn't playing that way with DU right now. It is probably coaching and the DU coaches want Butcher to play a more defensive style and work on his defensive game more... which that needs a lot of work. He is easily out muscled and isn't very good with his positioning in the defensive zone. He is a long ways off in those areas, and that is part of the reason that it will be well served for him and the Avs that he is going to college where he can get stronger and learn the game for 2-3 years (hopefully 3). That said his offensive skills are pretty damn good. He skates well, makes a great first pass, good shot that can get through traffic, and has a good feel for the game in the offensive zone. He has been really fun to watch this tournament.
As for the Eichel vs McDavid... I don't think anybody is beating out McDavid for the #1 pick. The hype is unreal on McDavid, and deservedly so. Still Eichel, Hanifin, Barzal, Strome, Konecny, etc are going to make for a hell of a top 10 in 2015. Hanifin and Eichel would be #1 picks in a number of drafts, they just happen to share one with McJesus.