The lower the number, the hotter it burns: the 1.8ohm replacements burn hotter than the 2.2s, which are hotter than the 2.5s, etc.
Some
e-liquids taste better when vaped at a higher temperature. So far, I like my coffee liquids when vaped on a 1.8 or 2.2 ohm evod head. At least one of my berry flavored liquids tastes "off" when vaped on the 1.8 coil, but it's fine on the 2.2.