young trees. In the photo above, I've taken a 2 foot long shoot and cut it into 8 inch long scions. While cutting up the shoot, I laid the scions down in order from the basal scion (top) to the shoot terminal (bottom).
There are a few things you should notice about these scions. First, note that buds are farther apart on scions cut near the base of the shoot. Also, the closer I cut to the terminal of the shoot, the more the scions take on a zig-zag shape. The best scions for grafting are relatively straight and have widely spaced buds.
The second thing to notice is that bud size seems to increase as you move up the shoot. This occurs as a function of shoot apical dominance. During the summer, the growing point at the top of the shoot actually inhibits the growth of buds near the base of the shoot. Bud size on a scion is not important to grafting success as long as buds are viable and firmly attached. Because of the apical dominance effect, basal scions are prone to losing primary buds and should be checked for bud viability.
The top 3 scions would be my choice for grafting. These sticks are relatively straight and have enough wood diameter to ensure grafting success. The 4th stick from the top could be used in a pinch but I would discard the bottom 2 sticks for being too small in diameter and too crooked in shape.