S_2S2 will be preferably enzymatically converted in product
Explanation:
K_mKm by definition is the concentration of substrate at half maximum velocity (1/2V_max).
A smaller K_m implies that the enzyme gets saturated at a low maximum velocity (V_max).
Therefore, since K_(m1) < K_(m2) and both substrates have the same initial concentrations, I would say substrate S_2 will be preferably enzymatically converted in product (will be consumed faster).