FF3 for DS, need help with job choice

‘Ello, puppets! I am new to this forum, and this is my first post. 😀
I was playing ff3 the other day, and I just got out of Eureka with all the treasure. I have a ninja in my party with Masamune and the Moonring Blade equipped. He’s pretty strong, but I can’t equip my strongest weapons to him (the Excalibur and Ragnarok). With his current equips, he has 230 attack power. If I could equip my best weapons to him, he would have 277! But in order to do this, I would need him to be a Dark Knight. This would mean that he sacrifices the special ability of ninjas. Or maybe I should just switch my Black Belt to a Dark Knight and equip the swords to him? Please respond stating your opinion.