We are using an Atlanta architect and he said copper, definitely.

We are in SC about 2.5 hours away and our builder used copper.

We have Pex with a recirculating pump.

There was one brand of Pex that had a bad batch. The problems showed up first in the hot water lines, especially on recirculation lines, precisely because the defective product had a heat impacted failure mode.

Recirculation pumps work fine with Pex other than that one situation. Copper has its issues, too. There is no perfect product.

We used Pex and we have a recirculator pump. It's far easier than copper, and cheaper. A couple plumbers told me they think some plumbers don't like it just because they can't stand back and look at all the nice connections and straight lines they made after plumbing a house with copper. I didn't know plumbers to be such an artistic bunch, but nonetheless, they didn't see a functional or economic downside to it.

Hmm. We'll be on well water and the local groundwater is reputed to cause holes in copper so we went with pex. We requested a recirculating system and the plumber said it was no problem. I hope he's right!

What do you understand to be the issue with pex and the recirculating pump?

There are issues with recirculating systems using copper. To avoid premature replacement (in as little as eight years) recirc systems must be carefully designed.

FWIW, I've only used copper. But the savings are so great on a large house that I may go to PEX next time around as PEX manifold systems are now common in luxury homes in my community.

Here is a link that might be useful: Copper vs. Pex

PEX can be configured in various ways:
"The unique properties of PEX tubing allow it to be configured in a number of different plumbing system designs including the typical trunk and branch system, but also in more innovative designs that include the home-run and remote manifold systems. The trunk and branch design has a large main line that feeds smaller pipes to each fixture. The home-run design utilizes a central manifold to distribute dedicated lines to each fixture. The remote manifold system runs trunk lines to small manifolds at grouped fixtures, such as a bathroom. The remote manifolds can be flow-through or closed ended. The different system designs offer opportunities to optimize the performance of the plumbing system, reduce the installed cost, and increase overall customer satisfaction and acceptance."

Nutherokie and fish...do you know which type of design you have?

This article may be helpful:
http://www.toolbase.org/PDF/DesignGuides/TechNote_Pex.pdf

My builder is also telling me that his plumber has been noticing more problems with call-backs for copper installations lately. He says there may be some quality problems with the copper which now comes mostly from Mexico. Don't know if there's any truth to this. Maybe some other plumbers can comment? I understand that the price of copper has gone up pretty high but my understanding is that there isn't much cost savings going with PEX because of price of the connectors. Is this still correct?

Ultimately I'm sure like most things in that it depends on the expertise of the plumber and what they have the most expertise using and installing.

On the copper pipe failures

"high water velocity exceeding five feet per second caused by undersized lines, over-sized pumps and multiple or abrupt changes in direction"

That is an incorrectly designed system. End of story.
Someone with little experience in plumbing design screwed up if they end up with flow velocity problems.

Copper is more vulnerable to water quality than PEX or CPVC, but does provide some bacteriostatic results when used in piping.

The plastic materials have all been observed to have bio-film form in them under some conditions.

Pick your poison based on water conditions (well water is a common problem with copper) first, and other considerations second.

Fifteen years with copper main delivery lines on a hard water well system...no issues at all. FWIU PVC has less chance of inside crud forming, galvanized is worse, copper is fair. I should live so long to see a problem!

"Fifteen years with copper main delivery lines on a hard water well system..."

Hard water is not usually a threat to copper systems, but kills water heaters.

pH is a common threat.

Knowing what the test results for the well water can provide needed information for determining what system to use.

We are in the process of a 3800sq ft build. We went with the PEX/Manifold system with each outlet having it's own dedicated line. Somehow the hot water circulates through the geothermal HVAC also. Not sure how it all works, but my DH said we'd have very low cost hot water in the summer. In our current house, it must take at least five minutes for the hot water to get to the master bath!

galvanized is worse

Is it even allowed anywhere? Here, if you buy a resale home, insurers require you to replace the galvanized or your coverage will be cancelled. Galvanized piping is in the same category as aluminum wiring, k&t wiring and buried fuel oil tanks.

While I can't speak for all PEX products, I can state with 100% confidence that Wirsbo/Uponor AQUAPEX can be used with recirc systems. In their "Professional Plumbing Installation Guide" (which I am looking at right now) an example of such an installation is described.

This is the product that we used when we redid our plumbing and it was great to work with. One of the outlets on the hot water manifold for the second floor is used as a return line for the recirc pump. The pump is controlled by motion sensors in the second floor bathrooms as well as via aquastat. That is, for 20 minutes from the last time motion is detected in the bathrooms, the pump will be controlled by the aquastat. All other times, the pump is off.

This has all but eliminated the added costs associated with the recirc system.

"I understand that the price of copper has gone up pretty high but my understanding is that there isn't much cost savings going with PEX because of price of the connectors. Is this still correct?"

Our build was fixed price. The builder gave us the choice of Pex or copper. Since we originally planned to be on a well, with the potential of ph problems, we chose Pex.

There was no price difference.

"galvanized is worse
Is it even allowed anywhere? Here, if you buy a resale home, insurers require you to replace the galvanized or your coverage will be cancelled. Galvanized piping is in the same category as aluminum wiring, k&t wiring and buried fuel oil tanks."

Galvanized pipe, aluminum wiring, and buried fuel tanks are still permitted by codes to be used by for new construction almost everywhere.

(Not that one would necessarily want to...but they are allowed.)

Even knob and tube wiring is still permitted, but only to extend or repair existing installations.
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For ease and speed of installation...Only PEX here.

Pex recirc here with no issues.

I'm interested to here how architects are plumbing experts.

In my world Pex is much cheaper but I don't have a home run system either. The connections are $2 at HD - I'm sure the plumbers pay less.