I think the main differences,other than appearance,are the type of activators
and the type of materials.Activators can be bottom button,mechanical side
switch etc...some are spring loaded and move independently to contact the
batt,others are magnetic with no spring and some move the batt itself into contact position.
I think the materials are chosen for 3 reasons:looks,texture and conductivity since some
things are better at letting current flow than others.
If you decide to kick a mod you are completely changing the function of it.
A kick will turn a direct current device,meaning whatever voltage the batt has is roughly
what you get to the atty,into a regulated device.Meaning you set the watts you want and
the right voltage gets delivered to the atty more or less constantly until the batt is too low to work.
Right now there are 2 types of kick that I know of.1 is the two versions from evolv vapor,
they use a ~800mhz type chip to give what feels like a direct current vape,it's very smooth at
boosting the voltage and some of us think it's the better vape.
The 2nd type from segeli and smoktech use the 33.3mhz (rattlesnake) chip and give you the same
type of vape as the Vamo,SID,Lavatube etc...they seem to work great for folks who use the CE
style tanks.
Wow,that got long winded huh?
Anyway I hope it helps a li'l bit