They are some differences as follows.
Different Material:PVC pipe is a pipe made from the polymerization of vinyl chloride monomers. PVC is a polymer that uses the lowest petroleum feedstock compared to other polymers. And HDPE pipe (high density polyethylene) is made of high density polyethylene.
Different elasticity：Compared with HDPE pipe, PVC pipe has lower elasticity. In order to make this PVC pipe elastic, plasticizer is usually used. But adding the substance is considered dangerous, so it is best avoided. If you want it to be elastic, you can heat it up a little bit, but that elasticity is only temporary as long as it’s still hot. And HDPE tube is very elastic, the general Angle can be bent without joint.
Fuction：Both have drainage features and only PVC pipes allow cold water installation. The HDPE tube can be used to install hot or cold water
Different prices:Compared to HDPE pipe, PVC pipe is cheaper.