You can see it in pass receptions, you can see it in his play off the board, you can see it in his positioning too. The defense off the rush is also slightly worse. Outside pivots on your strong hand are much tougher than on your off hand. Think about the radius of a stick and the encumberment of having the stick on the side which has the shortest path around you for an opposing player. For breakout, it means he has his back turned, the Kucherov hit is a good example of that too. He was left unprotected and of course the situation is worse than it could probably ever be because Kuch is a dirty POG but the play moves in his back, Matheson takes the rightful place of the left side D, Guhle has two choices, move the puck back and take the hit (what he did), or skate it up from his off-hand, which would take a fraction of second more than if he did scoop it up from his strong hand. Not a situation you want to be in. Then when he skates up, the stick is much closer to the forechecker, had he not move the puck behind him. All in all, he made the right play there, he was just a victim of being used on the RD and was in a lose-lose situation.
There's no defender that is stronger on his off-side, thats just impossible logistically. Of course Guhle is still good, of course he's still responsible, but he's just that much better on the left side. It's kind of like handicapping a player a little bit everywhere. Why would you want to do that ?