Better underload voltage on the 1600 than on the 2000. For mech mods the 1600 is ideal, the 2000 is ideal for buck-boost single cell mods, and the actual difference in capacity is only 200mah ( the rest of 200 is useable if you discharge the battery under 3.3v, and we all know not a lot of people enjoy vaping at 3v underload ).