one is not better than the other. If your ozone did not come with a venturi, then tap in to the air line up near or above the water line. jets low in the spa have more water pressure on then than higher jets, so they tend not to pull air in on low speed due to low water volume.
Best is get a venturi if you don't have one and tap into water line. Consult with the spa manufacturer or dealer first, then go to the ozone people. good luck