Articulation
Articulation is the ability of a toy to be posed and moved. The more joints on a figure (in either form), the more articulated it is. This includes the elbows, waist, knees, wrists, and even the neck of a Transformers.
For many fans, articulation is more important than even what the toy looks like; if it has an unusually high number of parts that can be moved, they will buy it over another figure that looks good, but can't move as much. One cheap (and increadibly effective) way of making a toy with a high level of posabilty is by giving it ball-and-socket joints on its shoulders and hips, and even sometimes the neck.
However, there is a certain balance between how articulated a figure is and how much it costs to produce; the more complex the figure, the more parts that must be assembled and therefore produced, and the higher the price it would cost to the end buyer. For example, Megatron (Armada) could easily have been given knees, and many kitbashers have taken to altering the figure to be more posable. It would, however, be much more expensive to do this in-factory, as the number of pieces needed to assemble Megatron's legs would increase quite a bit.
But many figures are more likely hampered in how well they can pose by their altmodes. Hot Shot's shoulders are harder to pose than most others because of how he transformes, many times only being able to move them in one direction (though his Energon figures were less articulated because of the ball joints in his shoulders, ironically). Conversely, others, like Unicron, have a higher number of points of articulation due to the fact that a larger number of parts have to be moved to transform the figure to begin with; his neck, shoulders, arms, wrists, hips, ankles, and even feet all have to be moved to change him from planet to robot and back. As such, many newer toys are finding new ways of having high posability, simple (but still interesting) transformation sequences, and impressive character models.
