Which acid is more effective in this reaction?

Either one, in an amount needed to stoichiometrically combine with the NaOH, will neutralize the base. Half as many moles of H2SO4 are necessary, but the H2SO4 will do more damage to the soil and its inhabitants. H2SO4 is a dehydrating agent and will have a greater detrimental effect on organic matter in the soil. Plus, any unreacted HCl acid will simply evaporate as water vapor and HCl vapor. When the water evaporates from a solution of sulfuric acid, a residue of liquid H2SO4 remains.