Each engine is totally different,you can't compare a low reving 4 cylinder with huge heavy pistons and long stroke to a high winding 12 cylinder with small lightweight pistons and short stroke.
As to which is faster, there are other variables such as traction,weight transfer electronic traction control,etc. My money would be on the AMG by a noticable margin ,in the real world a cobra doesn't hook up or stop anywhere near the #'s the AMG can.
Perry.
