Help with choosing weapons

So i need a bit of insight to choose my basch's weapon.

He is a bushi/knight. I know, his best in slot weapon is an excalibur but i am far from being able to get it.

Right now i have a ultima blade but am wondering if it is optimal or if the karkata and shield would be better.

What's your input on the matter?

I could probably also farm for a wyrmhero blade but i've heard its not that good?