In terms of frontal fire power it seems pretty hard to beat two cannon walls at 90 degrees to each other.
For instance this ship.
Not very creative but it is powerful in a front on battle.
It can also beats Tegs Rain Maker but it is a much closer battle.
It probably could go either way depending on the AI targeting.
The issue with diagonal designs is that the cannons don't have enough turning arc (I believe it is only 45 degrees). So if they are mounted facing outward they can't focus fire.
Lasers have much higher turn arc (at least 90 degrees) but their range is so short that they can't focus fire because they'll be out of range.