Which of XPE and PVC crawling pads is safer for your baby's health?

There are many kinds of crawling mats on the market. It is said that XPE is more environmentally friendly than PVC, but why is the price much cheaper than PVC? PVC cushion is softer and more comfortable. Is it adding too many chemicals?

Which material is safer for your baby's health?

Ask professionals (preferably those who understand chemistry / materials) to answer thesequestions, thanks!