Let me thank Racquet Sports Industry and Drew Sunderlin from which I quote from in different areas.

SWINGWEIGHT Swingweight, in simple terms, is what the racquet feels like in motion. A combination of too much overall weight and too much weight in the head area of a frame will result in a non-manueverable frame. Baseline players tend to prefer a high swingweight, while serve and volley players enjoy lower swingweights. Players with elbow problems are more comfortable with lower swingweights. Weight positioned at 6 and 12 o'clock will yield more power, but less stability, than a racquet weighted at 9 and 3 o'clock. Racquets with too high a swingweight will yield a powerful punch but may take too much energy to maneuver into hitting position, causing late contact and arm discomfort. Swingweights that are too low find the player consistently early on contact and prone to miss-hits, which may cause arm discomfort as well.

BALANCE Three frames all have 300 grams of weight.The first has 150 grams toward the handle, 75 grams in the throat area and 75 grams in the head. The second frame has 100 grams in the handle, 100 grams in the throat area and 100 grams in the head. The third frame has 75 grams in the handle, 75 grams in the throat and 150 in the head. The 1st frame is head light, the 2nd is evenly balanced, the 3rd is head heavy. the most powerful is the head heavy and theleast powerful is the headlight model. Think of the racquets as a hammer. The 3rd model is light in the handle and heavy in the head. Turn the hammer around (1st model) and try nailing with the handle. Tennis frames react similar when weight (lead tape) or silicone is added.

WEIGHT The more mass an object has, the more energy it can absorb. Imagine yourself driving a light compact car into a sherman tank. Which vehicle will have the most damage. It is well known the heavier the racquet takes less physical energy to produce pace and hit a "heavier" ball. This is provided you can maneuver the frame into position for the ideal point of contact. Not only will it yield more power, it will absorb more energy on the racquet. However you can't just have a heavier reacquet without regard to balance and swingweight.