Not too sure what you mean by which one is your main 'style' (larger or smaller?), but I'll critique the larger ones simply because I can't see how you might improve on the smaller ones technique-wise (their 'style' would only be apparent in their animations instead of stationary images).

Anyhow, it's clear you have a specific character design you want to convey with the top ones, I'm getting a sense of pillow-shading with the top characters (no clear light source on, for example, the girl's pants vs. her shirt since the light seems to be coming from the bottom on her pants but her shirt seems to have lighting from the top/front).

Additionally, the muted and highly desaturated overall sense of color these sprites have really crush any sense of vibrancy these characters might achieve otherwise, which in turn makes them difficult to appreciate at first glance. Even if they are meant to be on dull, muted/dark backgrounds, I think the over-use of pure greys/blacks is what's giving off that sense of dullness. Most sprites use either some mix of red or blue in their shadows/highlights to make them appear more vibrant. The only time grey tends to be used is when it is used as a buffer color, mixing between two values of different hues, on minimal palettes. Grey absorbs the nearby colors and, in turn, mutes them by stealing a bit of their vibrancy, allowing them to mix together.

Finally, the outline on the hair should be somewhat near the value of the body's outline in terms of intensity -- it's waaay too bright and gives a sense of the head popping off into the background. The only other issue I can see atm in terms of color is that the black outline on the body fights too much with the internal colors, so you could try lightening it up a bit instead of darkening the hair.

Lastly, the crotch area is much too low compared to the location of the hands for a human skeleton. They'd have difficulty keeping their topheavy body balanced if they were to walk. The wrists should end somewhere on the thigh area at least (but simply extending their arms would make them look more like an ape than they already do with their seemingly tiny legs, so you'll have to go the tougher route and lift their crotch areas up a bit to make them look believable).