I'm in no way an expert, but I believe you have it right.
I'm working on a project for a future Passive House in Maine and I just played around with the number on the PHPP, here's what I found:
I'm using triple pane Thermotech windows with Low e coating on surface #3 and #5 (exterior is #1), 90% argon, 10% air filled.
On my south facing wall I'm using glazing with solar heat gain coefficient (shgc) 0.61 and a u-value of 0.9
For a total area of 12.7m2 (around 110sq.ft.) my total heat loses are 2005 kWh pr year, gains are 3880 kWh pr year. ( a net gain of 1775 kWh pr. year)
Now if I change my southern windows to the windows that I intend to use on all other wall (shgc .37, u-value .71)
I get the following result:
My loses are reduced to 1743kWh pr. year, but my gains just went down to 2354 kWh pr. year.
I have one west facing window with shgc .37 /u-value .71. (glazing area is about 5.5 sq.ft.)
Loses are 100kWh, gains 58kWh.
If I change my western window to shgc .61/u-value0.9
I can increase the overall gains... Loses 114kWh, gains 95kWh, but...
I believe this will lead to problems with overheating in the summer when the lower sun (harder to shade) comes pouring through the windows in the late afternoon. The same I suppose is true for the eastern side. And on the northern side you obviously just want the windows with the lowest u-value.