Really? I find the Autobot version easier, I also find its easier to level up in the Autobot version.
I also find that its odd to do a mission where you need to destroy a certin ammount of objects, as the autobots. As for which version is better, I'd say Decpticons, to me its got a better story from the Decpticion's point of view. Its also got tougher missions, plus its just fun to destroy stuff. I mean, in the autobot version if you blow up cars and stuff you don't get experience for it