As a retired LEO, seen my share of crashes/collisions (not accidents, there's usually someone at fault). It just amazes me the stupidity of how some folks drive, I'm ever weary when driving any vehicle, I'm driving defensively all the time.
Looking at such carnage; I do not know the circumstances of these accidents, or who did what, but usually at least one driver in an accident is unable to control his or her vehicle and I can not help thinking that 4 wheel drive grip may have helped a driver control and escape at least some of the severity of an accident.
Take it from me Barry theoretic grip from 4 wheel drive is one thing - 'actual' grip from 4 wheel drive is something else. In 'extremis' where perhaps 4WD vehicle is doing violent manoeuvre's 4WD only magnifies the issues of one or more wheels not being in full contact with the road surface (in as much as an 'enthusiastic' driver taking full advantage of 4WD's supposed handling and braking benefits is likely to be travelling at a much higher velocity - and hitting other objects that much harder) In terms of braking benefits 4WD has nothing to to offer.....
All 4WDs are not the same and they are usually on SUVs which have a high C of G - Try an RS6 in the wet, nothing theoretical about that, If you have added traction you are not going to go off line when pulling away from the lights at full chat, like many performance cars do - A well sorted, well balanced low C of G vehicle with well proportioned 4WD has the thumbs up - the only downside is when you get out of shape, you are going much much faster because of the improved handling capabilities.
How many times have you snaked off from the lights on a power take off (in the dry), with the rear of the car changing the car's direction and you having to constantly correct it waiting for the speed of the car to catch up with the speed of the rear wheels - it does not happen in an RS6 even in the wet, it is traction and it is that traction that is there for you, to save you when you are on a bend and in normal circumstances would have exceeded your slip angle.