big german suv vs big german sedan

Opinion only, but a lot of it is simple physics. The mass of the vehicles dictates how much energy it contributes to the collision. The size of the vehicle and how thick zones are that can deform before an occupant starts to get a direct impact can be important in some circumstances. Where the centre of gravity is with respect to what is being hit can be important, a high centre of gravity could result in a roll over.

The vehicle designs now with air bags, seat belts, crumple zones, etc., key factors are more likely visibility and ability to avoid collisions than a large saloon versus suv…