Not sure exactly what series of aluminum car panels are made from, I highly doubt its 7000 series, probably a 2000 or 5000, maximum Yield strength for T6 temper is in 250-350MPa range. That’s still pretty soft.
Cold rolled full hard 301 stainless has yield strength of 1000 MPa. Tesla claims a 30x ultra hard, no one knows quite what that means yet, so maybe that’s 1500MPa yield strength. So call it 6-8x more dent resistant than aluminum at same thickness.
Tesla is using 3mm thick stainless. I can’t imagine standard car panels are more than 1.5mm thick.
Stiffness grows with square of cross sectional thickness.
So it is plausible Tesla’s panels are 20-30x stiffer than regular door panel.
That they could've made a dent resistant door out of aluminum.