
I think there's an advantage to be had in that design. Fear can reach beyond the range of any weapon I know of. And after all, isn't 'intimidating the enemy' a perfectly acceptable military tactic?
And believe it or not, I can TOTALLY see Megatron (with a different appearance) coming to Earth and, after a little Net search to find out what the squishy things are scared of, actually SWITCHING to that design. Now, I don't pretend to be an expert on Megatron's perspective and/or thought processes, but he seems like the type of dude who would intentionally choose to use the most scary and nightmarish design possible. What better way to strike terror into the hearts of your enemies than to choose something they already fear, adding instinctive terror to the fear they would naturally feel upon meeting you? Frightened enemies are easier to defeat, surrender becomes a lot more likely, and even the strongest foe is no threat when he's running away screaming like a little girl.