One obvious advantage of a 4x4 is that if you are stuck in a traffic jam of a million cars bugging out you can leave the pavement and go off road. You can't always do that in a sedan. However, I think the one factor that we have to keep in mind using a sedan is be more ALERT. At the first sign of trouble dont wait till you make sure. Slam on the gas pedal and move out to a safe distance before the crowds. Then you could stop and listen while you are far and safe from the immediate disaster area. If you do that you'd be OK in most cases. Just be sure that your sedan has a BOB and other stuff at all times. That is my plan at least since I drive a sedan about 75% of the time.

An oooold issue of FOUR WHEELER ( or perhaps a similar off-road magazine ) featured a road test in which a sedan was driven through a rough road and the test team had a SUV as a backup. The sedan went through without breaking any major part. It was stuck a few times but it wasnt too stuck to pull through. So, I think a sedan can do in many cases if you remember its limits. And I agree with norad that ground clearance is a big problem.

Another problem with most sedans is that they are not the least prepared for off road unless you have been thinking of such scenario. Not only they have low ground clearance and limited traction capabilities, but also they arent equipped with wiches or anything that can help getting unstuck.

I think it would be nice to put a sedan in our survival or bugging out plan. While we are driving through cities .. etc. we should take note of all possible routes and especially the ones that will remain clear and smooth during a disaster. While a 4x4 will give more options like taking a low-traffic dirt road I think in certian cases a small old sedan is OK because it looks more civil and less threatening to others as well as less valuable for predators who may think of taking your truck at gun point to use as a BOV for themselves. Not to mention that it is generally faster when you manage to leave the immediate damaged/congested area and want to get away ASAP to another town .