StarScream's design works like this...

I thought this would go unnoticed in another thread (Which, so far, it has), but it was too clever to be ignored, so here it is again:
Wikipedia [did] mention a simian design [for Starscream], which makes me think:
Have you seen simians move? They're faster and stronger than us, and better for climbing and moving.
The big arms probably add to the raptor legs in terms of running. Big arms would help Starscream move forward on his already superior legs, by way of momentum.
Think about it, when you run, don't you move your arms back and forth with every step?
Starscream's design is actually BETTER than any humanoid design in terms of movement.