for sub-ohming on a mech, the safer bet is to use the continuous rating. when vaping, for the most part, we are only pulsing. HOWEVER, this is in a perfect world scenario. all it takes is a faulty locking ring or a switch unknowingly coming apart for catastrophe to ensue. having your mod unknowingly *continuously firing* in your pocket with a load on it that exceeds its continuous rating, well...i think you know where im going here.
also, when you are exceeding your continuous rating, small problems can more RAPIDLY become big ones than if you had given yourself more head-room. you give yourself some peace of mind IMO and use the continuous.