Would it hurt more to get hit by a flat or inflated soccer ball?

Hi! I got into an argument with a friend recently about which would be more painful, getting hit by a flat or inflated soccer ball. I believe getting hit by an inflated ball would be more painful because more energy is transferred to you, since a flat ball will absorb some of the energy due to deformation. My friend believes a flat ball will be more painful because the time of impact on you will be longer, thus more time to experience the pain.

Online sources require me to pay to see the explanation so I'm wondering if anyone here can give some insights about it. Thanks for your time!