I always discard the terminal portion of the shoot when collecting scionwood. The terminal is crooked, has too many buds, and is nearly impossible to carve when grafting.
On the other end of the shoot, the basal piece of wood has very small buds which are prone to falling off the stem (yellow arrow points to aborted bud scar). I'll save this piece of wood for grafting because the secondary buds can grow into new shoots. However, when I'm out grafting and have a pile of scions to choose from, I'll choose this type of wood only after I've run out of scions with more robust buds.