the amplitude of a surface wave is proportional to 1/sqrt(distance)
the amplitude of a body wave is proportional to 1/distance

So the body wave disappears with distance more quickly than the surface wave. I'm not sure whether I worded my initial answer correctly.

Reason #1's applicability depends on the period (and therefor wavelength) of the surface wave. There are noticeable surface waves with periods as short as a second. But you're right, it is the impedance effect that is most important in the difference between the strength of shaking at the surface vs at depth.

My tendency is to strive for terseness because it is easier to proofread and clearer to read, although sometimes more difficult to write.