In my opinion the 3* seamless plastic balls are not as good as any 3* plastic balls with seam.
The Xushaofa balls are in comperison to other balls pretty round and hard but with the seamless balls you are not able to play as powerfull shots as with the plastic balls with seam and it is very difficult to play with a lot of spin, what you can do with non-seamless-balls.
So all in all i prefer the plastic balls with seam ecpecially those of Nittaku.
The Xushaofa balls are in comperison to other balls pretty round and hard but with the seamless balls you are not able to play as powerfull shots as with the plastic balls with seam and it is very difficult to play with a lot of spin, what you can do with non-seamless-balls.
So all in all i prefer the plastic balls with seam ecpecially those of Nittaku.