Sidious wins. His feats are significantly better, his powerscaling-hype-thematic placement is far superior, and he's just a better combatant. They may try sorcery but Sidious is hardly unfamiliar with that and really, his lightning is more powerful than their spells anyway.
With Naga Sadow it's closer, but honestly Sidious still wins as long as he can dodge his bricks without losing his focus.