IMO do the ones that relate to the structure of the house, like if you
want a family room that's 4' wider than normal, it's far easier to do
that at build time because of the permits etc. or a fireplace, or a
3-car garage. the other ones it's hard to say. carpet and cabinets
can always be upgraded later but you don't want to live with crummy
cabinetry while you wait for it to wear out.

if they have an energy efficiency thing (double wall construction) i'd
consider that, i think energy prices are going to continue to climb
rapidly.

(also when they build it make sure they do the Tyvek wrap correctly, if
you don't know what this means, find out)