I've got a new house to wire. It is about 5k sf. The HO wants metal boxes throughout. What is the most efficient yet best method of doing this?

Deep side-bracket boxes will dominate your install.

http://www.protectconnect.com/spinningProducts.html

These fellows ^^^ introduced the best thing going -- at the top of the market. Bad timing.

They would've been absolutely ideal for you.

They have now been quasi-cloned by the NEMA crowd. Read any recent copy of EC Magazine.

There are some nifty Romex-to-metal gadgets out there. I leave it to others who work Romex to rate them.

As for MWBCs -- they seem to be out of favor.

For such a large home I'd expect a hefty Service, 400A, and perhaps a sub-panel.

The latest trend in McMansions is towards star distribution -- of water, of data-com, and even of electric power.

It should be interesting.

IMHO, you may want to consider 4" square w/side brackets for ease of access with mud rings, as opposed to a 3-1/2" deep device box. It's faster to get in to bond, and a little wider on the sides. Easier to work with IMO, but either way, the $$ is much more than plastic boxes.

Include $$ for bonding the boxes. Green screws, pigtails, etc.

What reasoning did the HO give for metal boxes?? He may change his mind seeing the price.

It is rare,very rare to see metal boxes in resi.

Metal boxes? That's what I use! Both for customer service calls, as well as for rewiring my own house.

"Bracket boxes" dominate - standard depth 4-S boxes with the appropriate mud rings.

Correction: I use mud rings a bit deeper than I need, and set the boxes back to compensate. You'll want to make a spacer to help you set the boxes to the right depth. This practice means the drywall guy won't be fighting the screws on the face of the box, and things won't get beat up nearly as much.

Checklist: Boxes. Bracket boxes come in cases of 25.
. Mud rings
. Green screws w/ pigtails
. Cable clamps (boxes of 100)
. Mounting screws (short drywall screws are fine)

For dryer and range receptacles you'll want to use the larger 4-11 boxes, deep style. You can use a separate bracket to mount these.

Add to Renos comments that there are 4 square, side bracket boxes with integral NM and AC clamps.

The ho apparently enjoys building houses. He has a few 5k-7k houses around the country that he has built. He built one in Virginia that has 5 full masonry chimneys. He didn't like it so he built another and sold that one. He is very involved in the building process. He wants all metal boxes, copper plumbing, etc.

This is certainly a step up for me. I usually do smaller houses, remodels, service work.

I guess this is just a testament about how effective Carlon's marketing was. I am old enough to remember when electricians were fighting plastic boxes, swearing they would never use them. Florida pretty much makes at least a few of them mandatory if you are framing with steel studs. (another popular thing here)
You are required to bond steel studs and the easiest way to do it is with a metal box or a plastic box with a bonded metal mounting tab.