No Mace would destroy Malgus. Vaapad is THE ultimate form for fighting Sith. It uses the darkness within the user and the opponent to strengthen the user. But even without Vaapad, Malgus would be no match for Mace Windu. Just like Malgus is no match for Darth Sidious.
I think I need to watch these clone war cartoons to find out just what the heck is going on to make people so convinced about the unbeatableness of any characters that appear in it.