There's something to be said for a large frame vehicle hitting a small one. However, there are major trade-offs for this increase in hitting power:
1.) Increased stopping distance
2.) Reduced handling ability
3.) And most interestinly- poorer driver attitude
When you drive something enormous (Suburban, F250+), you are betting your life that your car will simply demolish theirs. However, unless you drive an 18-wheeler, there are always larger vehicles out there. If you need a people mover (more than 3 kids), a midsize SUV with three rows of seats will give you the best of both worlds.
The other problem is that many collisions don't involve other cars, rather objects of (relative to your car) infinte inertia. Objects such as- mountainsides, bottoms of ravines, water, buildings, roads (ie rollover due to operator error) and trains. Your Expedition is still just a speck compared to the punch those things pack.
Furthermore, a driver who is high up is more aggressive. Those soccer moms all chose to drive those vehicles, and look what happened to them! You feel invincible, but you aren't; this is how people get killed. Those who feel they are invincible will behave that way, and frequently with horrific results.
Therefore, if you are willing to pony up 40k up front and over time for fuel, get a sedan! Then, if safety is the #1 priority, equip it with a reinforced roll cage, bucket seats, and six-point harnesses. You don't have to be big to be safe.
-Penguin