Very interesting discussion.
From a theory standpoint a chassis that is less stiff in torsion tends to decouple or disconnect the front and rear suspension. So setup changes made to a softer chassis will have a less noticeable affect overall on handling. The old saying that you can't make a change to one end of the car without affecting the other is less of a concern here. So with a softer chassis there will be a wider setup window where the car will be driveable since the chassis is now a functional part of the overall roll stiffness.
For a stiffer chassis that window will narrow making that drivable sweet spot harder to find. Now you have to use shocks, springs, Anti-roll bars and roll centres to find it. Tuning a stiffer chassis means you need to pay more attention adjusting the front - rear roll stiffness balance, camber gain and the overall responsiveness. Find it though and you will be rewarded with a fast car. faster than you can achieve with a soft chassis.
The goal as with everything is to find that balance to what we as drivers can react to. Unfortunately not all of us have cat like reflexes, I know I don't, so either a softer suspension setup or something that does it for you like a softer chassis will help in that department.
The other consideration particularly with asphalt racing is the curbs. Watching the Euros on the weekend the curbs looked like they were half the height of the car and they were pounding off of them. Check out the second car in the pic. Pretty sure the front suspension would be close to bottoming out on that. In that situation having a softer chassis would certainly help keep the tires in contact with the road.
So I guess in the end it there may be a place for both. Just remember that marketing is a big factor too.