As a bisexual woman, I think Sam would be much better bi representation than Dean, In fact, I wholeheartedly think Dean is not bi and it would be awful if he was written as such in season 15.
Sam from the very beginning has been quite calm and relaxed when it comes to people assuming his sexuality and has never stated his sexuality, seems to be attracted to men (two crossroad demons he summoned were male) and is comfortable having close relationships with men, doesn’t specify the gender of his past partners, and is quite private when it comes to romantic relationships, meaning it would be believable for him to have kept his sexuality private if not in a long term relationship with a man. This isn’t even touching on the whole queer coded demon blood/psychic story line. The man felt like the black sheep in his family and so left to go to college in California where he could be himself, for fuck’s sake.
Dean on the other hand is very open about his sexuality, and very open about how he is attracted to women and only women. Unlike Sam, he has stated on many occasions that he is straight. Many fans claim that Dean protesting his straightness is actually him covering up his bisexuality. As someone who would closeted for a while and has been friends with many other closeted people, I can tell you that most of us won’t do this because it draws attention, but mostly because it makes you sound like you’re homophobic, which kind of makes you feel like you’re betraying yourself. Most closeted people just don’t bring it up and mostly keep quiet about it (like Sam). Dean constantly saying he is straight does not mean he is bi or gay. I also think a lot of the fandom’s belief in bisexual Dean comes from a lot of harmful stereotypes. I have seen people saying that Dean caring about his appearance and liking luxury means he is bi. Even worse, a lot of people claim that the primary evidence for Dean’s bisexuality is his promiscuity. There’s no problem with liking sex and there’s no problem with promiscuous bisexual characters if they are written properly, but a lot of the fandom believes that Dean liking sex and one night stands is good evidence for him being bisexual, even though all of these encounters are shown as being with women, is very harmful. If Dean was canonly made bisexual, this would just cement the idea that promiscuity = bisexuality, which is very, very bad and is the route of a lot of biphobia. Dean also sometimes does a lot of fucked up stuff in regards to sex - making sex jokes about underage girls, making jokes about peeping on girls, making rape jokes (mostly in regards to possession), assuming people want to have sex with him (turning up at Lisa’s door wanting to have sex after nine years; the porn star who left that behind and became abstinent and then immediately sleeps with Dean because one of the writers was clearly living out a fantasy; Kali saying no three times before Dean left her alone - I understand Dean being startled because he just opened his mouth and said no, but she was still very clear and he still tried to engage, just walk away dude), catcalling (when he was affected by the Mark of Cain, which strengths emotions), and slut-shaming a dead teenage girl (again while under the effects of the Mark of Cain). All of this is predatory behaviour, and seeing as there are homophobic stereotypes of gay people trying to seduce people who are underage and/or straight and uninterested, I do not want someone who already displays this creepy behaviour to be any kind of bisexual representation.
So, in conclusion, I empathise a lot with Sam and feel like he could be bi, but Dean is straight and him being bi would not make sense and imply a lot of shitty things about bisexuals.
