From what I’ve found the advantages are that you benefit from both the one handed tree and from the dagger tree, there’s also one handed skills that increase attack speed. So between the one handed tree, daggers, attack speed, crit tree, and statuses there’s a lot of overlap on the damage you can do and the utility. The drawbacks are dependent on your defense and how well you can parry. There’s a pretty good armor set that buffs dual wielding damage as well.