Here’s what chat GPT has to say on the topic.
A symmetrical spinnaker and an asymmetrical spinnaker are both types of
sails used for downwind sailing on a
catamaran, but they have different characteristics and are used in different conditions.
A symmetrical spinnaker is a sail that is the same shape on both sides, and it is typically flown with a spinnaker pole or a whisker pole. It is most commonly used when the wind is coming from behind the
boat, and the boat is sailing downwind. It is also typically used when the wind is light to moderate and the boat is moving at a moderate to high speed. Symmetrical spinnakers are generally easier to set up and handle than asymmetrical spinnakers.
An asymmetrical spinnaker, on the other hand, is a sail that is shaped differently on one side than on the other, with one side longer and the other shorter. It is typically flown without a spinnaker pole or whisker pole, and is most commonly used when the wind is coming from the side of the boat, and the boat is sailing at an angle to the wind. Asymmetrical spinnakers are generally more powerful than symmetrical spinnakers in these conditions, but also require more skill to set up and handle.
In summary, symmetrical spinnaker is used when wind is coming from behind the boat, and the boat is sailing downwind, while asymmetrical spinnaker is used when the wind is coming from the side of the boat, and the boat is sailing at an angle to the wind.
Also Asymmetrical spinnakers are generally more powerful but require more skill to set up and handle, whereas Symmetrical spinnakers are generally easier to set up and handle but have less
power.
It depend on the preference and skill of the sailor.