Just my thoughts based on my understanding of evaporation, I'm no expert and certainly can't predict the cooling values of various setups. I can say that evaporation happens at the surface of the water and increasing the surface can increase evaporation - drops have far greater surface for a given volume of water than a neat laminar stream does. Those laminar arc fountains are pretty aren't they, I wonder if there's a way to disrupt the laminar flow with a skimmer or something? hmm.

I just suggested the heating/cooling heat pump as an alternative. If you are putting in heat and it's not solar, heat pump may be cheaper to operate for heating than a gas fired heater.