One Handed vs Two Weapon for an Assassin

[noonedeserveshappiness]

Simple question. I think I'm going to play as an Assassin for my first playthrough. I wanted to know if people have found converting 20% of hits to crits to be more impactful than the boost to DPS from using two weapons. It's seems like it might be more useful to characters with assassinate, and work out to provide more DPS ultimately if you play right, but for some reason it feels weird to me to have nothing in the offhand, and just waste that slot, so my brain is resisting it. Thanks in advance.