Who would win Xemnas or Vader

Xemnas controls nothingness which he used to rip a city apart at will which Jedi, let alone sith (other than maybe sidious) never show that level of destructive capability with the force.
Edit: I also said base form Xemnas with all abilities Xemnas has shown period.

 

Xemnas couldn't manipulate buildings in the actual world, he did that inside Kingdom Hearts after absorbing its power.
And Jedi and Sith have shown similar power. In the Force Unleashed video game the main character is able to pull a Star Destroyer out of orbit, and Vader appears in that game and is able to match the main character in power. And he's even more powerful in Force Unleashed 2

 

Vader is ****ing Dead
DEAD
DEAD!

 

He grabs the buildings with nothingness, that was what I was implying. Also I am not saying that Jedi or sith couldn't do it but for them it takes massive effort and power whereas with Xemnas it is casual and barely takes up his time like the storm of blades that Master Xehanort manipulates in the Keyblade graveyard. also when they exited that world and fought in the true world that never was he summoned and tossed buildings at will so argument silenced.
edit: your example about the star destroyer it took massive effort to bring it down and to stop it from killing him in the process and he almost failed.