Polybutylene (PB) or cross-linked polyethylene (PEX) barrier for central heating

[cascas]

I have previously used hep2o (prefer to speedfit), but looking at toolstation, they do a PB and a PEX pipe. Both are barrier pipes for water & central heating. What are the pros / cons of each?

 

[Barry98]

not a sccoby doo , i only use copper , steel or hep20 at a push