Ok, so I guess I will weigh in on this. DISCLAIMER: I am a big fan of kingoflust. As a developer he has been accessible, tries his best to address and meet customer expectations, and he puts up with the legions of leeches and freeloaders that surround these efforts.
So the debate has been about the differences in the two paths, and how certain characters act in them. First, why would the actions of a character in one path ruin that character in a different path? That makes no sense. I will use an example: I have used illegal drugs (way in the past, very long ago). I can say with certainty that I did so because of who I was hanging out with at the time. Without that individual, I would have had neither the desire/curiosity nor the access to the drugs to make it happen. Since I have not encountered that person or similar people, I have not done drugs again. While my nature is generally negative to drugs, under certain circumstances/influences I guess I could be tempted again. This relates directly to Sunny. In general, she is what some might call prudish, as she has not in the past been sexually active. Then Marcus comes along, and 'suddenly' she is a cock whore. The key ingredient is Marcus and the temptation/opportunity he represents. Sunny is new to the area, wanting to fit in and have a good time. Marcus, good looking, fit and popular, starts giving her attention she has not been exposed to in the past. All of those factors come together to get her to try new things. And if the testimonies of Sophie and Maude are to be believed, Marcus is a first-rate cocksman. The MC, on the beta path, lets Marcus have every opportunity to be around Sunny and influence her, while Sophie certainly makes it apparent that Marcus is talented and that she doesn't mind sharing. Sunny slowly lets Marcus try some things, and finds he is indeed good at it. Things tend to snowball from there.
Contrast that with the alpha path. The MC knows that Marcus has skills, but is ultimately bad news for Sunny. He therefore shuts Marcus down at every opportunity, either making sure Marcus is not around or directly warning him to leave Sunny alone. Marcus has no in with Sunny, cannot influence her, therefore she remains the Sunny from the beginning of the game. The change then becomes the MCs influence on her. This influence will have to be more subtle and slow, as she is his sister, but he still has made some progress. Meanwhile, the MC is making more 'realistic' progress with Maude and Karla. Maude is just like Sunny. Under the influence of the MC, who supports her and encourages her dreams, Maude takes school back up, looks to the future, and is suitably appreciative to our hero. Without the MC, Maude's only 'support' is Marcus, who just wants to plow that ass. Since she has no big plans on this path, and Marcus is good at it, Maude slips back into cock whore status.
The point is, many people will act according to the circumstances they find themselves in. I for one see no correlation between alpha path Sunny and beta path Sunny, nor am I bothered by 'their' actions on either path. I will easily transition from the Sunny/Marcus/Tracy sandwich on the beta path (pure conjecture, but very much hoped for!) to the MC railing (in a loving way, of course) Sunny until she passes out, then heading down to Mom's room for round 2.
Thanks for hanging around for this. The game has developed methodically, but has a good deal of action in it to make it worthwhile, and it promises much more. If it is not to your taste, fine. This forum is here to air such observations, but do your best to be respectful to those who work and create. You can still complain, just be cool about it.