WA vs Primary stat

So "(total primary / total WA)" was close, just that

total primary = base + gear + MW (i.e. excluding potential)
total WA = your total WA

So if your primary stat was fixed, the more WA you add, the less 'primary stat' you need to equal 1 WA.

The main question I'm trying to answer is the following

"If you had a choice to add WA or add +primary to your empress equip, what would get you more damage?"

I assumed stuff like %atk and %primary would heavily influence that choice. I know it would vary person to person based on their own personal gears, but

K = primary / w.atk

Doesn't include those.