I'll give my 2 cents.
As a fan of neither team, i'll give my unbiased opinion.
Toews has a knack for game breaking ability. Something I've only seen in a handful of players. I've seen Toews take over a period/game and completely change the tempo. Keep in mind I've seen this against the Canucks quite often but I'll give you a few examples.
In VAN 2011 cup run when we were up 3-1 on CHI, it was pretty much a done deal/series. Toews went full ham, and clutched the next 3 games and literally set up Sharp with a glorious chance to end the series. I've seen him do this multiple times. I recall him taking over in the OT game against ANA in the playoffs this year and scoring the eventual GWG (CHI fans prob have a lot more examples).
As for Scheifele I don't see a young Toews. I see a very good top Center in the league who is going to put up more points than Toews IMO, but I have yet to see that game-breaking ability that comes from playing and leading your team in the playoffs year in-out. Scheifele albeit is young and has not had a chance to prove his worth in the playoffs. I just have a hard time seeing him being as effective against the top of the top competition that comes from a 7-game series. Facing the same teams #1 Defensive unit will grind a player down, I've seen Toews rise to the occasion, I've also seen him fall, and fall hard, but the ups outweigh the downs. (3 cup rings baby
)
tl;dr; I wouldn't trade Toews for Scheifele straight up at the moment (in a couple years, yes I would).