One thing I've understood about the Decepticons from the prequel Defiance, is that they were the defenders of Cybertron, so they know how to fight, so whether they are big or small, they all are dangerous.

With the Autobots, everyone apart from Prime, Ironhide, Prowl, Jazz(even though he died) were completely inexperienced, but as soon as the war started, they adapted and became skilful, so now they have warriors such as Bumblebee, Ratchet, Sideswipe, Arcee, her sisters, possibly Mudflap & Skids. I would say it's equal, they have their strengths and weaknesses in different areas.

 

Well Skids and Mudflap better make up for their size w/ a combining scene, that way they can be about Ironhide's size.