It'd be a difficult calculation to make. Bigger cars usually have better brakes and wider tires and in sporty trim levels of premium cars those can even help them stop faster than smaller cars.

Audi RS4 with it's sporty brakes, stops 1800 KG down from 140 km/h to 0 in 65 meters. Corolla 1.8 hybrid will do 130 to 0 in 66. Weighs about 1400 KG. Yes I cherrypicked it, but that's the point.

The extra weight actually helps grip so that cancels it out somewhat.

And yes, you'll be hurt more if you're hit by a bigger car at the same speed - but speed matters more (energy equals mass times velocity squared after all) and if the bigger car is able to stop faster, that means it's more survivable, assuming the driver or some driver aid system does indeed try and slow down the car - if not, then the heavier car is for sure more dangerous.