I prefer the marriage route because it feels like the one I can more easily take advantage of when I take control of the company. It just seems like it would be easier to expand the mining operations of the Nyrea with Steele tech resources if I'm married to her.
It's actually the exact opposite. If you're legally marrying Tavira, which you do in part by promising access to Steele Tech resources, she gets a say in how the company is run if you win. You're promising away some of your control in exchange for skipping the fight.
If you subjugate her, you can tell her what to do and she'll do it, which includes providing her with tools and instructing her to make use of them. That's the nyrean way.
The benefit of marriage is short-term, the benefit of subjugation is long-term.