This is hard to explain, but I might be able to approximate it. Our brains tend to decompose objects we see into salient features: in Example A, consider muscles, clothing, and hair. Naive artists often try to reproduce those features without giving enough thought to the underlying volume or dynamics, which leads to errors in anatomy, proportion, and shading, and severely limits poses, representations of action, and interactions between objects in the field. That all adds up to a flat, disconnected look in the finished product: think Trogdor the Burninator.

In this case there's more going on, too: the artist isn't trying to draw from life but rather to draw in a certain style (pretty clearly that of Akira Toriyama). That adds another abstraction layer: the artist is drawing a representation of another artist's visual vocabulary, without any apparent understanding of how that style works to represent objects. Doing so tends to compound all the errors above, and also carries the stigma of being common among pubescent fanchildren.

Example B is a messier piece of work than Example A and was almost certainly drawn more quickly, but it directly attacks volume, pose, and weight distribution, and doesn't try to translate through an affected style. Although it subjectively might look less appealing, that grounding allows it to be foundational to work that's much better by almost any standards, and therefore I'd be much more impressed if I saw it in someone's sketchbook.

(Source: am not a professional-quality artist, but am good enough to occasionally fool people into thinking I'm talented.)

I thought this was clear but a few people have been confused. I don't think I can explain it better than the followup paragraph already tried though:

"But the figures there communicate a good understanding of anatomy, a grasp of weight, decent composition. You can see from the third example, where the body turns and the shoulders overlap, that they're drawing what they see. You can tell that one foot is pointing towards the audience and the other is pointed to the right, even though both feet are a buzzy blob of lines."

Example A is floating in the air, not showing any realistic weight to how a body would fall, and each limb is sort of presented "flatly", instead of foreshortened.