<i>The thing &#x27;size&#x27; gets you is crumple zones. A bigger vehicle has a lot more material that can be engineered to deform and absorb the energy of the impact</i><p>Not the only thing. Recall your high school physics. Crank through the basic motion equations for inelastic equations. The more massive object experiences less change in momentum. All things being equal, passengers of the more massive vehicle are going to experience lower g-forces.