6-2 190 vs 5-9 170. That's a huge difference. Hughes has limitations defending that Dahlin does not have such as a longer reach/larger area he's able to defend, ability to consistently win 1 on 1 puck battles, ability to physically take someone out of the play/box out. These are Hughes' concerns and they are solely because of his size. They are pretty important traits for a guy you want to be your 1D. Mentally, how they process the game at both ends, there is no separation between Dahlin and Hughes imo
But it’s a pointless debate. He’s 5-9, he’s never going to have the size that Dahlin has. If Lebron James was 6-2 he wouldn’t be Lebron James, size doesn’t matter even close to as much as it used to, but it’s still important for a defender to have the size to handle the bigger skilled forwards.
Is Quinn Hughes going to be able to shut down Wheeler, Scheifele and Laine at 5-9? I highly doubt that.