Pound for pound in my experience I would say convict. That being said I have a Jack Dempsey not even close to being full grown that just added a decent sized Dovii to it's hit list which now stands at 8. I call it Jack The Ripper.
It seems everyone is talking about breeding and aggression. What about not breeding?
Also African aggression seems to be reduced by over crowding, but CA cichlids IME aren't as simple. With a lot of CA cichlids its an individual thing. I had a male convict that wasn't very aggressive at all, but they are known for their aggression.