Having tried to write both, I have to say that I much prefer doing - and reading! - something which is plotted and structured. I think it gets the reader more involved if you are introduced to a character and watch them change, and then how other people react, etc.

Although I think most people who would answer this kind of question would probably tell you they prefer plotted and structured stories, recent evidence seems to suggest pretty much the opposite.  I personally have two- no, three- stories that are essentially chapter stories and- while they've been reasonably well-received- they get very few comments or views when compared to the shorter, self-contained stories and vignettes I've done.

I would also note that if you are thinking of writing a longer story and posting it a bit at a time-or as you complete each chapter- something that may help you to maintain interest would be to set some sort of dramatic goal for each chapter.  Think of it like plotting a serial television show; there's enough going on in each episode to keep new readers interested, and enough carry-over that long-time readers start to see the over-arching plot develop.

I think that in many cases AlexG is correct about why so many stories never get finished; if you're writing a story out of a desire for a vicarious sexual thrill, then the moment of climax is pretty much what the 'story' is about, and anything after is a waste of effort.  I would add that I think a number of authors get frustrated by the apparent apathy that seems to go hand-in-hand with the ease of point-and-click reading; readers can, with just a few clicks, visit a story, read what they like, and click away without ever being inconvenienced or feeling any impetus to leave a comment.  When we- authors- see that our stories have been viewed X-many times and received 2 comments, we get discouraged and decide that our time can be spent more profitably in other endeavors.

Well, when I talk about a fully structured and plotted story, I don't necessarily mean a novel, or even a novella -- a work of any length can have a fully developed plot. I use the Blake Snyder method, which was developed for feature films but the essentials of which apply, really, to any good story. It is as follows:

1. Opening Image: This is the "before" in the "before and after", our very first glimpse of the world our readers are to see.
2. Theme Stated: Pretty self-explanatory, someone usually actually says in so many words what the story is about, and usually says it to or in the presence of a main character.
3. Setup: An expanded version of our opening image and how our main character/s fit into it. This is where we usually introduce the Big Problem faced by our main character/s.
4. Catalyst: The message or event that ignites our main character/s need to solve the Big Problem, Right Now -- sometimes by introducing an even BIGGER Big Problem which arises from the previous one.
5. Debate: Where our main character/s have to decide whether he/she/they can and/or should go on the adventure to solve the Big Problem.
6. Break Into 2 (Act 2 -- remember, this was originally conceived for screenplays): This is where our main character/s make that decision.
7. B Story: A change of pace, usually lighter in tone than our A story, where the main character/s meet someone who imparts (to the reader if not to the main character himself) a new perspective on the overall story.
8: Fun & Games: The meat of the story. In film, this is where the "trailer scenes" come from; in the femdom/femuscle genre, this is where most of the "scene" takes place, be it wrestling, L&C, FMG, whatever. Most -- not all.
9. Midpoint. Exactly halfway in the middle of the story -- the main character/s either enjoy a major (though not final) victory here or a crushing (but not permanent) defeat.
10. Bad Guys Close In: Whether literally (opposing forces LITERALLY getting physically closer to our main character/s) or figuratively (conflict between main character/s or main character/s and supporting friendly characters)
11. All Is Lost: This is a definitive defeat for the main character/s. It should APPEAR to be complete, absolute and total defeat. The best All Is Lost moments include, in some way, the "Whiff of Death" -- death of a character, a goal or an idea doesn't matter. SOMETHING either external or internal to our main character/s must die here.
12: Dark Night Of The Soul: Our defeated main character/s come to fully understand their defeat in this section. This is where all hope has been lost, the main character/s know it and we must suffer this knowledge with them here.
13: Break Into 3: Something is said to or remembered by our main character/s which recalls what they were told in Theme Stated. The main character/s get their second wind from this.
14: Finale: This is generally your second major action section. Armed with the renewed inspiration of Theme Stated and tempered with wisdom gained through All Is Lost and Dark Night Of The Soul, our main character/s now get to kick ass and take names.
15: Final Image: The "After" in the "Before and After" -- should simultaneously be similar to and diametrically opposite of Opening Image.

Yep, and that's where your title and log line come in. Those are a whole 'nother monster, though. Grabbing your readers is actually pretty easy, especially in a small, specialized market like this one. Nailing down who your audience is really isn't that hard when your audience is maybe a million or two, maximum. Once you have them, though, once you get them to Page 1, keeping them with you all the way to the end is the trick.

The "scene" part, though, is just the sizzle. Now it's true that the sizzle is all some folks want -- but give them a little steak with it and pretty soon they'll feel cheated if the sizzle is all they get.