Its around 5% worse but it varies depending on rolls. Tsurumaru gains a more significant lead when you can 3 hit (i.e. cor present). Its not only in SoA zones, Tsurumaru should still be winning by a small amount outside of Ionis.
Cibitshavore R15 path C is best bow by far, hardly any call to use Namas Arrow now. Only real situations where you use Yoichi are Kamihr Drifts and Ceizak delves.
If you are determined to keep Yoichi on and sacrifice 12 str and 7 store tp so you can retain access to a weaponskill that has been relegated to piercing bonus only, then there's not much point in asking for set advice.