In all 3 of the movies, to me, at least, the Decepticons all had a different theme for each different movie. In the first one, they were all named and difficult to kill, so they had a sort of Black Hawk Down feel to them, kind of a small squad of soldiers fighting to the death. In the second movie, they were greater in numbers and much more deadly, not only killing several soldiers and The Bike Sisters, but having the combiner Devestator and The Fallens mystical powers. They also had a clear objective, being activating the Sun Harvester. So they still had a military feel to them, just this time, an entire army instead of a small squad. In DOTM, they felt the most threatening. They invade, and they take over. Several squads of Decepticons are dotted around Chicago, like the execution squad with Soundwave and Barricade. They also still had a military feel, but also a very alien one. The Decepticon ships that latched onto the buildings? I've seen frogs do that to aquarium tanks, and it gave me the creeps every time. Personally, I prefer DOTM's Decepticons. But which are your favorite?