I have always found Ewoks to be the worse of those two. They look and act in many ways like teddy bears, so people will naturally desire to cuddle up to them and let their guard down. Then they can come in with the same worrier aggressiveness and make a kill before you can get your guard up. The Gou'ald on the other hand, come in with all the signs of a worrier race that has only one thing on their mind - to kill you. This will cause one to raise their defenses, which makes one harder to injure and kill. They might even be able to injure or kill some of you in the process.
Battle of the years: 1000 or 2000