No, what you are suggesting is a situation biased towards Darth Malgus, a battle of power vs power Malgus loses, considering it's the only fair way to judge these things without showing some biased towards/against one or more characters, this is how we must argue these points.
To take two characters into a vacuum and pit them against each other removes many of their possible strengths. Sidious' greatest asset was arguably his ability as a master manipulator and deceiver. So arguably he would see through Malgus' trap and set one of his own.
But some people are saying that no matter what trick/allies/giant space slug/what have you trick Malgus could attempt, that Sidious just gets to auto-win cause he is just so awesome.
Its still Sidious, no matter how many ways you slice it. It will always come back to Sidious. There is no "what ifs" there is no "Buts" there is no "What about?" NO, there is NOTHING that Malgus holds above Sidious.
Clearly there are many what ifs, buts and what abouts that could give Malgus an edge.
Malgus, riding the deathstar that is being driven by Batman for instance.