Tomorrow we wrap up on a game at work and I get time off for a couple of weeks. I'll try to push a personal image out of me (hard to do pixel art after pixel art, heh) to illustrate my point.
As to the main question:
"I agree with that. The ultimative question is however what we gain from using it, where it's more powerful and where it just sucks in terms of efficiency. I am interested in finding that out."
The main thing it would help beginning pixel artists with is to STOP them before they put down a single pixel. Make them consider it a brush stroke instead. A brush stroke has a direction.
Time and time again I arrive to some pixel-specific technique that turns out to be well-known in the larger theory of fine art. Not to say that the latter is a consonant space, there's various different schools of thought that are not compatible. But at least the concept exists somewhere there in the wider world of art that before you gesture at a canvas, you are considering the direction, weight and nuance of the gesture (of course the subconsciousness plays the larger part, but that's a nonfactor for what we're discussing here).
This is what this excercise is meant to illustrate. Pixel artists hold at their hand two amazing tools that other artists not often have, and almost never both of them at the same time:
1. minimization of physicality in drawing. You are not directed or constrained (or in the flipside, startled by) the subconscious drives of the body, as expressed through your moving hand on the canvas. So many people that are terrible with pencil and paper go on to become good pixel artists because they can plot down pixel after pixel, they do not rely on smooth movement from point A to point B
2. completely opaque, completely predetermined atom-level control of the picture. We sacrifice fidelity and in trade we get big, fat pixels that we can visualize before we even put down the first one. We can't visualize the whole image (difficult skill to train, real artists do train it) but we can certainly visualize a cluster, and with practice, a collection of touching clusters.
There are specific limitations and benefits to having these two elements in our art. Nearly all great pixel art shows telltale signs of how it was created (and that's another reason it's so trivial for a trained eye to spot reproductions/copies/photoshop jobs masquerading as pixel art).
But beginning artists get lost in the art, they immediately begin SCRIBBLING. And then they salvage their scribbled thing with antialias.
This excercise is meant to stop people from scribbling. It's meant to teach them traditional art skills they'd get from proper tutoring that are specifically applicable to our discipline. A different path arriving to the same destination (which is, control, intentionality, visualization before action). Trad artists would go from general to specific. I struggled for years trying to apply general to specific in an organic way in pixel art and never could. I'd put down something vague, then zoom in and work on a corner of the image. Get my palette from that, and go systematically through everything using that invented palette.
It might have been alright and some of the art thus produced might be good in the eyes of others (or myself, sometimes) but that doesn't mean there wasn't a step missing.
Cluster theory was something I worked on to find a way to structure the middle part of creating a pixel art drawing. Not the heavy aa-finish, not the initial rough sketch, but the part where you're building the volumes and conveying the shapes. That's where clusters became a solution.
The excercise I'm suggesting here is a mental one. It's trying to help fix a step before clusters even occur. When the clusters are just in the mind. Ideally, one would consider the shape before they lay it down. But even if you go in and fix an older image after the fact, the mental training is there.
re: efficiency. The end result is less bad moves. Less pixels you have to fix. Less aa to take out later. Less blurriness introduced you then have to take out. Working with what pixel art has: sharpness, clarity of color, confluence of edges. Not working with what it hasn't: softness, transparency, vague shapes, smooth gradients.
I appreciate the capacity of an artist like Cyangmou that can put in pixels a blurry field of view effect. I do not say it has no place in pixel art (what does that even mean?) I am saying that for people that have gaps in the beginner and middle steps of creating something with pixels, they should consider not just bigger clusters, but their smallest ones. A single pixel is not a cluster.
As to what is gained from applying this technique: yes, the image will have harsher shifts, and will appear more blocky. Compromises will be made. But I think what is gained is a stronger gestalt, where the form and the content of the image are better aligned. A piece of craftsmanship that is declaring what it is, not playfully hiding what is is by showing it can emulate what it isn't too. To take a picture that has unpleasant blockiness but a promise of gestalt into a picture that retains the gestalt but has a pleasant blockiness is a matter of experience within that mindset. I am too, working on this.