The appreciable difference of .2 ohm is almost zilch, especially with VV. I guess the only nice thing on a 1.6 is it does actually work (though looks plain silly) on a standard ego/evod battery. I seriously think a lot of these .2 delta type coils are their (mfr) way of handling variance. I suspect they try to build 1.8 and the ones on the high side get sold as 2.1 and low side 1.6...
Just a theory of course.