PEX is my preferred material. It's been used long enough to have an established track record and it's a good one.

No cases of leaks due to rodent activity? Aside from cost, why should I choose PEX in South Texas?

Here's a decent list of copper pros and cons: https://www.expresssewer.com/blog/can-copper-piping-cause-plumbing-problems-7-signs-of-trouble#:~:text=Although%20it%20is%20highly%20resistant,and%20lead%20to%20pinhole%20leaks.

https://www.sharkbite.com/us/en/resources/blog/the-sustainability-of-pex-vs-copper

Verbo, what do you mean by "land of concrete slabs and pinhole leaks"? Copper is well known for lasting 50+ years. The copper pipes aren't run through the foundation, so what does the slab have to do with anything? The water at the build site will be basic (7.2-8 pH) due to all the limestone. Basic water doesn't corrode copper.

Do you not have rodents in your area? They are known to chew through PEX.

https://www.houzz.com/discussions/3466640/pex-and-rats

Ned,

Having lived in both South Texas and Central TX, I can tell you that a comprehensive pest management program to include rodent control, termite control, control of scorpions, spiders, etc. is a really good idea whether you choose copper or PEX for your system.

If water leaks in a crawl space, does it make a drip noise? Slabs are impervious so sure leaks matter.

How does your kitchen island sink (big presumption here) get water if not through a slab.

"The copper pipes aren't run through the foundation, so what does the slab have to do with anything?"

They are installed in the slab and buried in the concrete, and when they need to be replaced the slab gets busted up.

If leaks in PEX are a concern (and their track record suggests they shouldn't be,) PEX tubing can be installed in conduits in the slab to facilitate their replacement. Copper? Not so much.

Copper is installed in slabs, and the reaction between the alkaline cement and the copper causes pinhole leaks. It is a well known phenomena. There are communities all over the South that have to replace copper with PEX at about 20 years of age.

The kitchen island is an exception, but I was told that the piping only runs through the foundation at the water main entry point, and then is routed through the attic and walls (1 floor house). Is that a non-standard approach? Should I be asking for it to be run through the foundation to every bathroom fixture and laundry room?

I would've assumed that code requires everything running through concrete (other than PVC sewer pipes) to be in a conduit, be it PEX or copper. Some concrete, for example, contains steel fibers to prevent cracking. Seems that would be a problem for PEX as well as copper pipes.

TileDesigner, haven't slabs and copper been in use across America for a long time? Why would they just be finding out about the problem you mention in recent times?

My plumber put larger pex in the slab (3/4) that would allow to fish a 1/2" through if there was ever a problem) and then did insulated copper above grade.

There is some recent hubbub about PEX pipe failures. Can't find some articles I had heard about, but here is a blog schilling for themselves on that problem:

https://www.flowguardgold.com/en-us/blog/blog/dont-flex-your-pex-how-bending-pex-pipe-can-lead-to-premature-failure

The main problem I have with PEX is the fittings. I don't know of any gasketed seal that doesn't deteriorate, whether in plumbing, vehicles, or elsewhere. If everything is homerun though, you can reduce locations of failures. The type of fitting matters, here is another website (schilling again, but hits some points I don't have to type) comparing Sharkbite to crimp:

https://www.answerthehome.com/pex-crimp-vs-sharkbite/ the key point to take from this article is number of years for those fittings.

If anything, pro-copper and pro-PEX sides can come together and agree that CPVC is the devil.

I built a house in FL this past year. PEX does NOT go through the slab, except in places like an island where it goes through a conduit in the slab. I'll look for a photo of some of the rough plumbing. Now the drains, yes those go through the slab.