Go with whatever one you personally like the most, as it's your creation, but I agree I do like number one the most. Number 3 looks like quality was lost. and actually looks more unrealistic to me than one. 2 the colors are too similar for my taste. you can argue which tree in the forest is best for as long as you want, and drive yourself crazy.

In numbers one and 2 you lost some depth in the legs, and now they look like they are joined together, like a mermaid or a short dress or something. I think the key to this artpiece is to not overthink it, or overwork it.

The first one is very detailed, you can visibly see everything it's supposed to be, and have, clearly. It has depth, curves, lighting and shadows. 2 and 3 lost that, it became more flat and just looks sort of unrealistic.
I personally liked the over aliased look of the first one because it actually looks like her skin is ICY. It has a nice shine to it. Thats just what I think.

However for the smaller version, I would go with number 3.

If I'm quite honest, I can't really think of anything much to improve on this. The style and colors are great. I like how visible the details are already. I'd call this a job well done.

Hair is good, only problem is the color is over saturated/ 2 bright.

Good job, your first sprite looks like a shitty space station 13 sprite. The next one I can actually tell its sasuke so you've stepped miles away from your start. Good job.  You're working on a small scale so thats also good. Remember to work on a medium colored background, and work with less harsh colors. The blue on his shirt is too intense, and his hair is a bit too gradient. Keep it up and you'll eventually get your desired goal.