Recently I watched The Departed and Infernal Affairs. Infernal Affairs is a Hong Kong action classic; The Departed is an Oscar-winning American remake. Both movies are fantastic. I watched both partly because I love good movies - I'd already seen The Departed, and I've seen so many Hong Kong movies that I learned a few simple words in Cantonese from context - and partly because I wanted to do a comparison study.
One contrast I noted: the cop who goes undercover as a gang member gets a backstory in the American film, concerning family drama and family ties to organized crime. This doesn't happen in the Hong Kong version. It's not necessary to the story.
Another contrast: in both versions there's a confrontation between the mob boss and the high-ranking police officer investigating him. The Hong Kong version makes this necessary to the story. The American version doesn't.
Still another: the American version combines two or three women into one. The undercover cop's relationship with this woman, in the American version, is necessary to the story. In the Hong Kong version, none of the women play any kind of crucial role.
For background, I've been writing screenplays every couple of years since I was a teenager. My first scripts were very, very bad. One of their worst features: incoherent, rambling plots. I look back on them, and even though I wrote them, I can't figure out why one thing is supposed to happen after the other.
This made me very concerned with economy and necessity in screenwriting, and I took an austere hard line towards action and necessity in my scripts. My last spec happens almost entirely in real time. No flashbacks, no fades. I didn't plan it that way; it just emerged as a byproduct of this obsessive prioritization of economy and necessity over any other feature of story-telling.
My screenwriting rule: the greater focus on necessity always wins. Any un-necessary element is banned. But if this rule is really the way to go, you'd expect it to describe a corresponding pattern: the movie with the greater focus on necessity is always the better movie. But that's not what happens. I think the rule holds true in this case for only two out of these three contrasts.
The Hong Kong confrontation is much, much better than the American confrontation. There's no necessity at all in the American confrontation, and confrontation without necessity is just chest-thumping. The American version integrates the one woman into the movie as an essential piece of the story; in the Hong Kong version the two or three women, well, let me put it this way, I can't figure out if it was two or three. I know it was at least two, but there's this girl who the undercover cop may or may not have unknowingly fathered, and her mother may or may not be his former psychiatrist. I couldn't tell if the actresses just had similar faces, or if it was supposed to be a very subtle subplot.
This ambiguity and confusion is the whole reason necessity matters in screenwriting. A movie is like a really well-done presentation about something that never really happened. You're putting together a line of reasoning, and if the line of reasoning makes sense, people get what you're saying. If it doesn't, then they don't.
However, the backstory contrast doesn't seem to me like an argument for necessity-only screenwriting. The American version's backstory is unnecessary, but it makes the undercover cop a more interesting character. The Hong Kong version's cop is basically just a guy doing his job. The American version gives us an unusual person doing an unusual thing for very personal reasons.
I've also encountered this same contrast - between structurally necessary elements, and elements which appear to be superfluous ornamentation, yet which in practice deepen the experience - in the context of dance music.
Here's a pair of mp3s I made tonight. In the first mp3, you have a simple loop. In the second mp3, you have that same loop, plus several changes, mainly bassline texture and sound effects - bleeps, blips, zaps, squeals, voices, and filter sweeps. The added changes make the second version much more interesting to listen to. It sounds more like a finished track.