Agree completely. I've never been a big fan of forced submission, willing consent is the ultimate aphrodisiac in my opinion.
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is a great example of a dev that understands the differences and is trying to mold the story so it can appeal to both types (only pet/obedience is in atm and slave/forced submission route is planned for an upcoming version). There is also the side of BDSM that I didn't touch on which is physical punishment heavy vs light and both can be used regardless of dom/sub intentions. In that instance say both ex and sister really enjoy physical pain and it helps them orgasm, you might go for a dark route for ex focused on public humiliation and emotional manipulation but not physical pain, as she hurt you emotionally your punishments target her emotionally and deny her the cathartic release and pleasure that physical pain would bring her. Sister on the other hand gets the light hearted pet treatment but also things like whipping, extreme contortion, needles, wax play as it makes her happy and excited to be stimulated in that way by someone she loves during intimate moments to draw them closer but it isn't necessarily used as punishment (unless its more playful punishment, like she did poorly on a test at school after you tutored her and its a game rather than because she genuinely displeased you, which can also lead to her intentionally messing up to be punished again and again).