Sooooo, proportionality.
I've stuck all the edits next to each other and drawn, in beautiful magenta, some stick figures over them.
So while your new edit certainly improves upon a lot of things, it also has a worse pose and proportions.
Note that Seiseki's edit uses your belt to just hang over the bottom of her butt. It's not actually a belt at this point and more like a ring in a different colour. This was an interpretation of your original edit where you could imagine it looks like she's wearing a belt below her ass, and then the dress does crazy things once it's free.
Enter your edit.
Here we see you've fallen back into the idea that the belt is a belt and her butt is below it, but this makes her torso look hella long and her legs very short. Zia interpreted this as a chibi character and so left the legs short, but shortened the torso and arms significantly to get her more proportional (though as Gil points out, perhaps a little too short).
I added one last edit to this example just to show her with a more regular body shape.
One other thing is that Seiseki's edit has a lot more "character" in her stance. The arms are pulled back, the chest is pushed forward and the hips are further apart and facing the screen more. This gives her much more of a presence and personality.
Try imagining what kind of personality you would like her to have and then work out how she would stand based on that. Practice in the mirror a bit to really see some examples and get the proportions right (if you're a guy just remember that girls have shoulders that are only about 3/4 the size of your own and very small rib cages).