I think the most damaged part of my car is behind the right front wheel. Any sediment from puddles smacks that wheel first. I get more dirt accumulation on the sides of the car as well.
I think different cars are different as my wife's Focus's back end gets filthy.
My hood has more pock mark damage than my trunk, but my trunk appears to have more microscratches since I try different things out of my hood and it's nearer to where I hang my obsession light.
I think hood and trunk are just some of the first thing you see when you look at the car.
I'm planning on next year about this time gettign brave enough to wetsand.