Bow have a bonus against flying mob, while xbow doesn’t, I don’t recall now, but I think xbow have block penetration bonus (need confirmation its been a while since I played).
Also, some classes/skills only work with one or another.
Musketeer and Cannoneer only work with their specific weaponry.
Musketeer = Musket
Cannoneer = Cannon (off-hand so you will be using with xbow)
Hackapell require a sword in the off-hand (the class have an attribute for it).
You have to consider also that the content ahead of your current level will determine your weaponry, many get Isbality + Manamana due to holy damage (most open world dungeon mob is dark property).
I have a wugushi and I still use Viper due to most mob in the fields being earth/poison property.
Gearing on this game is situational imo. You will find lots of people using cloth armor to increase mdef for certain areas and changing to plate for other parts.