Broken sword is worth it if you want the exp boost. stats for it don't matter since you can get to a point where your character does a crazy amount of damage, especially when you're using the cracked essence to help with growth during combat. I've been maining the broken sword and cracked essence ever since I got them.
The only thing that really matters for weapons is the skills, and it's entirely dependent on the build you want. With the broken sword's skills, you can both give or take away from your stats for the fight. It's basically a "do I want to be stronger or weaker for this fight" kinda thing.