The 1HS+Shield vs 2HS Shadowknight debate

[Quizlop]

Every time you successfully hit an enemy they get physically pushed a little bit, so it's possible to interrupt casting by having a bunch of people beating on the mob while facing the same direction. The amount you push the enemy with each attack is the same regardless of what weapon you use, so a faster weapon will let you push a mob further in a shorter period of time and increase the chance that they will fail their chanelling checks.