If I was building a house, and provided it would not violate any kind of code (can't see why) I'd make the outside walls double 2x4 studded walls, with a seperation between the 2x4's. Basically, two walls very close to each other, maybe equivalent to like a 2x12 in thickness. Fill that up with batts of insulation, maybe some foam too for the first wall section. Though I don't know if this would be like having two vapor barriers since there is also plastic that would go over the wall before the drywall.
Also the roof type has a certain effect on insulation. For example my house has a roof where the overhang is lower then the ceiling. The slope of the roof creates a "dead zone" where there is little to no insulation at the very end of the ceiling. I would love to have one of those heat cams to check that out, bet it is a major heat loss, and probably an issue for any house with a roof like mine.
I would personally avoid something that is very new and not yet widely used. It might be the best thing to come out in construction history, or it might turn out to be a flop, and you'll only know in 10 years from now, kinda like Chinese drywall.
I believe the double wall thing is called an envelope house, but I may be wrong.
you could do a 2 compartment wall (I'd stagger the studs if you do that to cut back on the stud transmission), and stick the questionable spray foam on the ouside half, and whatever on the inside.
you could always do the ICF thing, and add some foam sheets or whatever to the outside.
you could do an earth home.
there really are a million different ways to get a super insulated home. most of them involve thicker walls.