windows are the weakest part of the wall, the lower the shgc & ufactors are,
the better the window. itrw purchasing different shgc & ufactors for different
sides (orientation) of the house is another problem. unless you plan to make
sure yourself that the right window is installed on the west side vs north side
it is better to buy the same window for all sides.
just what I've encountered over the years.
don't believe that the installers
actually understand the difference between anything other than window size.
and invest a little time in reading flashing directions that come with each window unit.
you can be sure that the installers will do the flashing the way they have always
done it. we have lots of water intrusion here from that old X cut into the housewrap.
good flashing info on each window...if someone reads it and makes sure it is done
properly.
what is your insulation package?
for walls, I perfer foam sheathing on exterior, conventional insulation in walls
and air tight drywall approach to interior.