The 0.6Ω mesh coil is specially designed for sub ohm vaping, it has a large mesh inside, giving a faster heating process and massive vapour clouds.
The 0.8Ω Mesh MTL coil is as the name suggests, designed for MTL vaping but will provide a higher output of vaper for a stronger hit.
The 1.4Ω regular coil is designed for MTL vaping, for which you can enjoy a throat hit with similar to smoking.
The 1.4Ω Ceramic coil is designed for MTL vaping but works better for those who like to chain vape a little. This is due to the ceramic material coping better with higher temperatures that might be seen with heavier vaping.