I've tried to pick the least graphic images possible:
http://img.radio-canada.ca/2015/08/09/635x357/150809_kr04b_v... from http://ici.radio-canada.ca/regions/saguenay-lac/2015/08/09/0... -- which ended up killing the two occupants of the car.
This one is interesting because you may very well hit the moose facing forwards: http://www.snopes.com/photos/accident/moose.asp
I don't think there is much to be gained in terms of safety. Let's not forget that while you may have large moose, there's a range where they can still be much smaller while growing and still damage smaller cars fairly easily.
Roof landings don't always end well -- my Civic was trashed when a deer basically bounced up and collapsed my roof on the passenger side. My head would have been trashed as well had I been a passenger!
In general, if you cannot stop, hitting something head on is the best bet. Modern cars are designed handle that sort of collision with maximum passenger safety.
I'm not sure about moose, but with more nimble animals, swerving is no guarantee of avoiding collision. A deer can change direction quicker than an automobile, and if it had any sense, it wouldn't be running across the road in the first place. It's definitely safer to slow down and honk your horn than it is to try to guess which direction the damn thing will jump.
[EDIT:] When I was learning to drive, my father often recounted the story of a hapless acquaintance who, in swerving to avoid a snake, had precipitated a loss of control that killed her infant child. He's not a big fan of swerving for animals.