I'm still debating on switching to slush from kano.
I actually have one s9 on both.
I cant tell which one would be best

Why do you need to go away from kano? Slush is taking 2% fees. Compare it with kano's fee these days. And AFAIK there has been detected a few years ago that Slush's pool was making some strange manipulations with pool's hashrate, so I can't fully trust to Slush's pool now.