Which piping to get for LPG copper or plastic?

Hi I am getting my kitchen remodeled and want to put my LPG cylinder in my balcony to make the house more safer. I have been recommended to get a copper piping or option of plastic piping. The copper piping will be done by a professional and plastic can be done by my carpenter. Cost is not the issue but I want to understand which is better option and safest.Not sure. please advice.