Quoting: GMDannyB
If we are going off of their career by the end of it? They are probably both right above Power. Slaf and Celebrini I believe will be better
Dahlin is an elite 1st pairing defenseman, there's no way he should drop on this list. He plays against the best every night. Here's a simplistic view of the first 2 seasons post draft (to match Slafkovsky's career so far).
Hischier: 151, 37-62-99 +10 (0.66 P/GP)
Dahlin: 141, 13-71-84 -20 (0.60 P/GP)
Slavkovsky: 121, 24-36-60 -32 (0.50)
Power: 87, 6-32-38 +13 (0.44)
Hughes: 117, 18-34-52 -29 (0.44)
Honestly Power looks like the better pick right now too. Hughes had a pretty weak start to his career though so maybe Slafkovsky can become an 80-100 point guy, but I don't see the elite skill that Hughes has.