Well, chlorine dries out your hair and if you are blond, you hair will start to look a little green. If you use a curling/ flat iron, etc., they should not be used all the time. Heat styling is drying to your hair as well and can also burn the ends. IDK which is worse, but if you swim or style your hair using heat often, it can damage your hair. Hope that answered your question. :)
Both chlorine and heat styling are bad for the hair. However, chlorine is worse because it drains off all the natural moisture that is required for healthy hair. You can prevent the adverse effects of chlorine on your scalp by rinsing your hair with clean water before exposing yourself to chlorine water. Clean water will help in the absorption of chlorine.
It depends if you use the special shampoo and conditioner or if you go over your same strand of hair multiple times with a heat styler i personally think it depends on well ... Do you swim more or heat style more???