Well your not going to be blocking Yagluth so I would take silver sword over crystal axe. If you miss a strike it's gonna be a lot spent stamina where as if you miss with the sword recovery is easier. You need speed for yag fight now since he can attack fast and his fire rolls you even with fire pot.

Other than that if you want a challenge go the crystal axe, or use a silver knife. I've done silver knife yag and plains so I assume crystal axe would be a similar affair in difficulty.