PEX A is the far more flexible material between the two, and it has little or no coil memory, giving the installer the ability to repair kinks with a heat gun. PEX B however, is stiffer and so, noticeably harder to bend. Any kinks in PEX B pipe can only be repaired by cutting the pipe and installing a coupling. Though they both have similar resistance to oxidation, PEX A has a high rate of chemical leaching making it a concern for plumbing installations. PEX B is a clear winner in terms of its price and that it has a higher bursting pressure, which is very important for plumbing installations.