Ohms affect the wattage and current that your coil will pull from your battery. What battery/
mod do you use? If it's a VV/VW mod than either will probably work fine, if it's a fixed voltage mod (mechs and simple egos) then it depends what you're looking for. The 1.6 will produce a bit more power (more vapor and flavor, hotter, increased chance of dry hits) than the 1.8, and you might like that better.