Interesting to hear how folks do it in different areas of the country. Most everyone in Maine uses the black PE pipe coils--when shopping it sometimes helps to tell associates you're looking for "well pipe", then they take you to the black stuff. PE, HDPE, LDPE--the names give a glimpse at how adaptable the polyethylene monomer is for chemists to work with and tailor the polymerization and formula to resist whatever it is they are looking for it to do. The PEX is a different cross-linking arrangement of the same monomer that gave it some great strength and stretch qualities--I don't know what it did for abrasion resistance.
I wonder if fail rates have to do with old formulas, overexposure to UV or heat, poor handling and installation, or just a bad batch or formula that didn't quite do what was planned? I know the coils can be challenging to handle, but I'd prefer a straight shot without joints, FWIW.