We learned in grade school that the proper angle to maximize carry is when the projectile is sent off at a 45º angle (regardless of initial velocity) to account for gravity. The reason that this is a simple example is because there are no outside forces that factor into the equation.

The launch angle of a golf club is much more complex as you have the added component of the golf ball and the lift that is created by the initial ball velocity and dimple pattern of the golf ball. Because of the lift created by the golf ball, the initial ball velocity should be much lower than 45º. To provide an example, the touring professionals are normally looking to launch the ball between 11-14º, while golfers with much reduced swing speed should launch the ball possibly much higher. (Note: The loft of a golf clubs does not denote the launch angle the ball will come off the face)