I beg to differ. Where would the extra shock absorbtion come from? A radial wheel is a bit stiffer laterally, so are you saying that it's the sideways flexing that's helping to cushion the ride?

You're certainly not going to find much difference in radial cushioning.
Spoke deformation in total is measured in fractions of a millimeter, and for a normal low-flange hub the difference in spoke length between radial and 3X is around 10 mm, about 3%.
Do you really think it's possible to detect a difference of 3% of a fraction of a mm (that's attributed to the spokes) when youre riding on, say a 23 mm air chamber?