For people to give you intelligent answers, you need to let them know what kind of boat you have. It would make a difference as to whether they would recommend symmetric or asymmetric. A Hobie 16, for example, usually sails straight downwind rather than tacking downwind -- or at least tacks downwind at very deep angles. So it might be more likely to benefit from a symmetrical spinnaker. Cats with daggerboards or centerboards that tack downwind at greater angles and have more leeway resistance benefit more from an asymmetric spinnaker.

Maybe rephrase your question with boat type.