The higher the bounce, the easier it is to rally. There is more time to retrieve and play your next shot. It takes more skill to score. There is more movement, as rallies generally get longer. Good length is considered the foundation of the game.
The lower the bounce, the harder it is to rally. There is less time to retrieve and play your next shot. It takes less skill to score. There is less movement, as rallies generally get shorter. Good length becomes less important, with the emphasis shifting to short balls.
For an illustration of how bounce affects the game, here are the flight paths from the drive test.
All of these drives come off the front wall with the same velocity and flight path, but rebound differently after the first bounce. Which of the drives are the easiest to retrieve, and give the most options for the next shot? Which skill levels get the highest surface temperatures with the Pro?
A player retrieving the 114f Pro has all her options open. She can take the ball before the back wall, or stroll back to play the ball after it hits the back wall. If the ball is played after it bounces off the back wall, it will be relatively easy to play a variety of shots.
A player retrieving the 103f Pro can play the ball after it comes off the back wall, but will have a less luxurious situation. There is less time to cover more distance, and there is less room to execute the next shot.
A player retrieving the 93f Pro has lost most options after the ball bounces off the back wall. This ball is best retrieved before it hits the back wall. This gives the player less time, and requires better ball judgment. More skill is required to a play variety of shots from this situation.
A player retrieving the 84f Pro must come on to the ball early, as the ball will die on the back wall. This drive presents the fewest options, and requires the most skill.
The lower the skill level of the player, the lower the ball judgment and ball control. When lower skilled players get less bounce, which is typically the case when the Pro is used, they get an extra penalty. They will have less time to retrieve the same shot compared to a better player, and end up playing a more difficult version of the game. The lower the bounce, the greater the penalty, the more difficult it is to rally.
As it becomes more difficult to rally, rallies typically get shorter, which usually leads to a further decrease in surface temperature. The lower the surface temperature, the easier it is to score with short balls, moving the conventional wisdom of squash from "good length" to "go short".