Pex is far superior. Make sure you use copper or brass fittings and connections. Also, be aware that all connections are interior to the pipe, and therefore you functionally loose one pipe size. We have ( in the construction business ) found that installing 3/4" pex instead of 1/2" gives us the equivilent water pressure.
I re-plumbed my OTAS with PEX after a kitchen remodel and used Seatech fittings. These fittings do not have a barb inside the pipe and do not reduce the ID at the fitting.
Pressure tested (air over water) at 150 psi when installed and now at 14 mos and 10 trips since installed I've not experienced any leaks period.
No tool required and easy to remove/reuse the fittings.