We are currently using two interpretations of Guardia di Testa.
Experimentally we found that the version on the left is superior as a static guard. That is to say, when you just lying in wait to either bait your opponent or just catch your breath.
The one on the right makes more sense as a dynamic guard, specifically a parry. While reinforcing the sword with the buckler gives you a stronger guard, there isn’t necessarily time for that.
Ultimately it is important to remember that guards are supposed to be used as waypoints. No matter how you catch the opponent’s blade, you’ll want to transfer it to your buckler so that you can make launch your next attack.