I'm not trying to be a twat but a lot of it lies in installation. I would believe that sweated joints are more reliable than a Sharkbite. But I've really seen a lot of shitty welds that leak. Sharkbites also need to be installed properly, and Sharkbite failures are all installation error and not mechanical failure. The pipe was deburred or pushed in far enough.

I've always been against PEX v. copper pipes but apparently PEX is better! The original fittings were crap but the new ones are apparently very reliable and the PEX is less likely to burst when frozen.