Neither.
With cartomizers, it's usually the filler that burns.
http://www.e-cigarette-forum.com/fo...8-4081-etc-filler-type-cartos.html#post301709
http://www.e-cigarette-forum.com/fo...1-etc-filler-type-cartos-510.html#post3460582
To avoid, or at least minimize, your chances of frying the filler, make sure that your cartomizer 1) is properly filled with juice--it has to be kept wet at all times, 2) that the resistance of your cartomizer is appropriate for the voltage of your battery (high wattage vaping is not recommended), 3) that the cartomizer is not reused too many times--they are disposable and were not designed to be refilled and reused many times (they can generally handle 5-6 ml of ejuice, not much more).
Also, I recommend that you always have at least two or more cartomizers in rotation, especially if you tend to chainvape--they need a little rest time every three or four puffs. Do not overvape.
Good luck!