Assuming that the two cars are the same mass (you didn't say), I'd guess that they'd each do an equally distributed total of 150kph of damage to each other. The fact that one was moving faster than the other doesn't matter. It could be 10kph + 140kph, or 0 + 150, or 75 + 75, and the damage distribution would be the same.

If they're different masses, I'm sure it gets a lot more complicated.

And by the way, I call "no SUV flamewar" for this thread right now, because I can totally see it coming.