If we go on Bangel vs. Spuffy, the former is more adult imo. To quote myself from other threads regarding the topic.
Adding to this. It's a HUGE pet-peeve that one of the first arguments against Bangel is "That was HS puppy love. and Spuffy was real"
Ok. So I guess it's HS puppy love when their relationship had struggles such as losing each other, almost dying for each other. Buffy nursing Angel back to health when he returned from Hell. Talking about her future with him. Her having to talk him down from killing himself. etc.
Most HS puppy loves don't involve half the things they had to get through. As individuals or a couple. Even in real life, many HS sweethearts have married. Meanwhile you have grown adults in their 0's who bounce from relationship to relationship and don't know anymore of what they want than some High School kids.
Using a classic example. Sitcoms.Cliff & Claire were a couple since HS. They were married throughout the show with 5 kids. But I guess because it started in HS, their relationship doesn't count? After all, they couldn't possibly have loved each other in HSS?
Another Roseanne x Dan Connor. Dan was the first & only man Roseanne was ever with. She lost her virginity to him on their second date. When he had his heart-attack, she's very vulnerable and says the heartbreaking words that she's worried to lose than man she'd been with since she was 15. I guess their relationship isn't true. Again teens can't know what they want & love someone/
My own parents. are an example. My mother has known my father all her life & has been with him since she was a teen in the 80's. They got ,married not long after she turned 18. Not to say their marriage hasn't had it's share of drama. lol But that's every relationship. However, note that I said DRAMA, not ABUSE & TOXICITY. There's a difference between those things.
Bangel was the former. Yes the relationship started when Buffy was young, but that doesn't mean they weren't experiencing the real thing. Buffy was 21 in season 7, and she still refers to her feelings for Angel as love. We don't have 21 year old Buffy saying anything like "Oh well Angel was only a crush" or "I thought I loved him but I was too young to know better." No. Buffy after having more life & relationship experience, losing her mother, trying to raise a child & support a house, still says she loved Angel more than she will anything.
And if we're gonna pick on age, then even season 7 Buffy doesn't know any better. She outright says she's cookie dough that hasn't fully baked. She says the last episode she's not finished growing yet. And that includes her relationship with Spike. He got cookie dough as well, by Buffy'sown words. Plus 21 is still college aged. How many college students have fully matured, when they're not out drinking, partying, and going through the phase of doing all their stupid stuff.
Bringing the comics into it it, Buffy is probably in her mid-late twenties in those and possibly 30 at the end. She STILL retains feelings for Angel. She had a fantasy about being chained naked to HIM and Spike. She was slightly jealous when Dawn was hugging him & talking about her crush. Puppy HS crush wouldn't be lasting until someone is damn near 30. lol
And, Buffy & Spike could be together whenever they wanted with NO limits. And the mutually chose to split up because they don't work without crisis. THAT seems more like teen love. Without the passion & danger, there's not much left. And Buffy even said that in season 6. Spike says great love is wild, passionate, and dangerous. It burns & consumes. Then Buffy tells him it burns & consumes until nothing is left and that love isn't lasting. And we see it in season 12 when they decided to split due to things being too peaceful. That sounds exactly like immature "love" that runs on passion or how worked up you can get each other -good or bad. It's about what you can feel in pleasure rather than feeling for someone else.
Meanwhile Buffy & Angel never made the choice to not be together. They just accepted that it was already decided that they couldn't be. They tried repeatedly being together only for something to stand in the way, and when they were together, there were tons of limits. Like sex. How many people going through just puppy love are gonna try to make a relationship work that they can't have sex in? Most horny teens won't be down for that. it takes love to entertain the thought of trying to be together without every getting to have sex Even adults don't want sexless relationships & won't stay in them. They'll either separate, agree for the able partner to have other lovers, or cheat.
I think the narrative needs to be dropped that Bangel was all about puppy-love & non-serious HS romance. Nowhere was their relationship treated as such in canon.
When Angel comes back in season 3, he's weak & Buffy is caring for him & bringing him food. Buffy could cry to Angel and be vulnerable with him and have him understand her feelings. As opposed to Spike who she tried to keep emotional distance from, and emotional tears her down by encouraging all her worst traits, and telling her those things are all there is to her, and by not accepting it, she's lying.
I suppose Spuffy is relativistic in the sense that some relationships are abusive & toxic. lol But just because it's abusive & violent, I don't automatically equate that with "more adult." I just equate it with all dysfunctional relationships, which adults & teens can have.
Then when Whedon comes back to the comics, he didn't do the ship any favors. season 10 + 11 are spent building Spuffy back up, then Joss has them break up for reasons stated above. So it reads like they were always sexually interested in each other, and tried to give a relationship a go based on that. And true to form when all the dysfunction was gone, and the fire died down, it became clear there wasn't much left besides friendly fondness. Bangel never ran off of passion & Intensity the way Spuffy did.
The way I see it, Bangel was a romance & relationship.
Spuffy was dysfunctional f**k buddies who let sex play with their head. And that sure does happen in real life when couples try staying together because the sex is great. Again difference between loving how someone can make you feel from time to time vs. how you actually feel about them.
In fact, it's like Sam x Diane in Cheers. They were as dysfunctional as couples come, and all they had was sex & heat, but no substance. It was hard to believe what they saw in each pother besides that. In the series finale, Sam admits that they had great sex to the point of needing to do CPR on each other, but besides that they weren't good together and just proved it when they met again.
Sex, passionate, and intensity can be good or toxic depending. But those things don't automatically mean a relationship is more adult, imo. Even as a casual sex affair, it was immature & more complicated than casual sex should be. If we go on casual sex, Faith was a more mature example than Spuffy. lol
You can argue both as fantasy.
Bangel is more the softcore female fantasy.
Spufffy is the hardcore dirtier male fantasy.