The answer is quite simple, when you think about it, Master Xiannarr. This is the same question as who would win between Darth Nihilus and Darth Sidious.
If they are in the same system, Darth Nihilus, in this case our Emperor Dreadwar, wins. This is due to Hunger, and their opponents not being Wounds in the Force.
If they are not in the same system, Darth Sidious, or in this case Emperor's Voice Vassago, wins. This is due to the Wormholes and meteorological anomalies that can be created via Force Storm.