One molar $\text{(1}\text{M)}$ aqueous solution is more concentrated than one molal aqueous solution of the same solute. In solution, ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ provides three ions. While $\text{NaCl}$ provides two ions. Hence, vapour pressure of solution of $\text{NaCl}$ is higher (as it gives less ions). Therefore, $\text{1}\text{molal}\text{NaCl}$ will have the maximum vapour pressure.