RC,
The most important factor, IMHO, is the ratio between WBC and Y seats.
NW 744--- 65:338 roughly 1:5
NW 332--- 32:211 about 1:7
NW 333--- 34:264 about 1:8
UA 744 (FC/BC)--- 87:260 about 1:3 (and 1/3 of Y is E+)
UA 777 (FC/BC)--- 61:198 about 1:3
There are way too few WBC seats on 332/333 which makes upgrade extremely impossible. Therefore NW could not afford any SWUs like UA because the demand for WBC is so high. The consequence is that high mileage international flyers (100k/yr) leave NW. Who wants to sit in NW's cramped Y for long international flights with virtually small hope of upgrade and no E+? This is a huge mistake by NW in my view.
NW should carefully design 787 and maintain at least 1:5 or even 1:4, 1:3 WBC/Y ratio.
As a math professor, I pay particular attention to numbers.
Thank you for doing this!