I know this thread is a little old now, but when I do appraisal work on new construction certain things stand out to me.
Cleanliness. I know its a construction site, but some builders are adamant about keeping the site somewhat presentable. They have periodic cleanings, they fine for leftover food/beer trash, use tub protectors, put down mulch for a walkway to keep out mud, etc. Builders who do this typically have a higher standard that carries over to their build process.
Framing. Size of joists in the ceiling, spacing, connections, etc. Some of this is mandated but some builders go beyond.
Electrical. You would be shocked at how I've seen light fixture receptacles mounted.
Inspections. Some builders outside of required inspections use third parties for their own inspections.
Then of course you have standard features. Go to the sales office and ask for the standard features list. Of course many builders have different tiers and price points, but compare multiple builders at similar price points and find out what is standard. Gutters, masonry, sod and irrigation, base flooring, base countertops, cabs, and appliances, wall surrounds (tile vs fiberglass), and the list goes on. What does a base house buy you? This is usually how they differentiate price points in a neighborhood as well as lot frontage.
At the end of the day, a lot of big builders have homes for high end, middle, and low end. I would stay away from those focused purely on volume, low end series homes.