Swingweight "only" matters when you are swinging in a circle about some axis -- which is basically most of the time. Swingweight determines how fast you can accelerate the racquet. The swingweight of a racquet is an indication of how much torque you must apply to the racquet handle to get the racquet to swing. The value of the swingweight is determined by the amount and distribution of weight in the racquet. A low swingweight is very maneuverable. A high swingweight is less maneuverable but more powerful for a given swing speed. Swingweight is also a good indicator of how much weight is "behind" the ball at impact. Of all the parameters discussed above, only the swingweight is not created equal in the sweetspot. The racquet with the highest swingweight will most likely be more powerful in the sweetspot during a normal swing about an axis like your wrist, elbow, or shoulder (stringbed stiffness being equal). That is because the ball will behave as if it collided with a heavier object and, hence, moves and rotates that object less. The amount the racquet is accellerated when it is hit is related to how heavy the racquet behaves (not how heavy it actually is) at that point. This amount is known as the "effective weight," or "hitting weight," at the impact location. The faster the impact point accelerates backwards, the lighter must be the effective weight. The effective weight is indirectly related to the swingweight, and most of the time, swingweight can be used as a stand-in to predict results.* Swingweight is therefore the only parameter that is intrinsically related to power at all impact locations. It is also the only variable that is related to maneuverability in almost all swings. And it is the only variable that can, under the right circumstance, cause an increase in power by being smaller (faster swing) or larger (more oomph behind the swing).