buffrider,
I've very little experience with this, but from what I've read it also depends upon how the bark reacts to having needles plucked. If the bark tears and then bleeds sap then it is better to cut the needles down to about 1/8 of an inch. Then the cut needles will turn brown and fall off when they're ready. Cutting the needles prevents sap from bleeding, potentially weakening the tree and maybe attracting nasty creatures, like borers, to the tree. But I am unsure if the tree physiologically reacts differently to the two procedures.
Hope this helps,
Ray