KK & Fraylim did a story for Joe Six-Pack called The Boy's Guide to Girlhood and without trying to spoil it, I imagine that's a bit like how you're describing Sweet Marissa.
Sort of, but I think the tone is different. It's been a while since I read Boy's Guide, but despite the protagonist being "stuck as a woman", there's a passiveness to the main character that is, in my opinion, what makes that story weak. Or at least for me, it makes the fantasy unfulfilling because it doesn't really capture any of my submissive kinks. Let's be honest, MOST of SixPackSite stories are like that. Very bland characters and lots of passive allowance of being feminized.
Sweet Marisa is forced feminization. The level of cruelty may very well turn people off. But it knows what it is and it entertains some of those scenarios that the submissive part of my brain fantasizes about. That's why, even if it's not a story that's my usual cup of tea, I respect it because it commits to what it is. I recognizes just how fucked up the scenario should be for someone to have forcibly feminized someone else and doesn't romanticize it or downplay that.
I'm a believer in the idea that a reader should be sent home happy.
For me, I believe the reader should finish the story "satisfied". Now that doesn't mean that the ending is happy or sad. But there should be closure of some kind. If I'm in the mood for a story where a husband gets cucked, then the satisfying story progression is that the husband gets cucked. But the story should know what genre it is and know what audience it's writing for. It's why I rant about stories where the ending tries to justify it as "Look! They actually do like all the fucked up shit happening to them!". I think you need to EARN that kind of justification. Otherwise, you've slapped the ending from a different genre onto the one you've currently written.
I usually prefer social feminisation over sexually feminisation processes, as they tend to be methods (in my mind at least) that stick better for the main characters journey into womanhood. For example, in Mirror I feel Elenas female friends and their expectations of her should be a better way of conditioning her to be female in her daily life than the once a week sex session Nikos has with her.
Generally, I don't think one is inherently better or worse for delivering a good feminization story, I think this all boils down to whether the arc the character goes through passes scrutiny. That said, I think that too many stories equate "sex with man" and "being a woman". Especially when they don't go through the emotional aspects. I feel like feminization and how that relates to sexuality can be just as powerful and internalized as much as social pressures. Speaking personally, my own journey experimenting with vibrators, dildos, and exploring my body in "non-masculine" ways was powerful. But it's true most stories don't pay off that level of detail. Most of them just go straight to "Oh wow, sucking cock for the first time has made me a cock addict! Me so girly now!".
Along these lines, did you read Emory Ahlberg's "Anywhere But Boring"? Without giving too much away in case you haven't read it yet, I'd be curious to hear what you thought of that. Personally, I really enjoyed it.
I have no issue with people winding down roads and finding themselves in the end. I've known friends that were convinced they were straight, then bi, then gay, then ended up in a heterosexual marraige after meeting someone they fell for. Does that invalidate their journey? Absolutely not. My own journey with my gender and sexuality, how I present myself is also winding and nonlinear and at times contradictory. But those are
real stories, or stories meant to be real.
I think Anywhere But Boring is well written enough. While I find some of it a bit contrived (and there's certainly scenes I'd workshop a lot more), I understand what story it's trying to tell. But I don't think it's a feminization story. It's a trans story (and I think it knows its a trans story). There's nothing wrong with that. But for me personally, I'm really not interested in trans stories (in the same vein that I don't enjoy most coming of age stories based in real life in general). For me, I find it uncomfortable getting into the actual personal lives of someone else (even if they're fictional). It feels intrusive and disrespectful to treat as erotica.
That's why I generally dislike "sweet/sentimental" stories. The vast majority of them either feel too intrusive, or come off as glurge. It's like encountering toxic positivity. Having a story go "yay, all I had to do was transition, and now my life is perfect. I'm hot, everyone that matters accepts me, and I'm married to the perfect significant other" just rubs me the wrong way. Either because that's not reflective of real life, or because it's such clearly wish fulfilment from writers that are projecting too much. It, again, makes it feel incredibly intrusive.
By all means, have a happy ending. But let's earn that happy ending. Let's have a premise that makes sense for the story we're trying to tell. And let's be clear with our genre. I think the main "ding" I'd give Anywhere but Boring is that while in hindsight, I realize it wasn't meant to be a feminization story, it does start off like one. So it is a bit of a "bait and switch". But to its credit, with hindsight you do understand that the story knows what it is. And so I'll give it props.