It's a subtle difference, but I keep going back and forth and I need a second (or more!) opinion.

Also, do you guys see any stray but blatant mistakes anywhere? I try to get all the weird pixels but sometimes after a while everything starts looking the same...

I'm leaning more to the left. I like the cooler white and pink, and feel that there is a stronger contrast + better harmony. The more defined highlights on the horns adds to it too.

Also, I'm not seeing any stray pixels on my screen.

Thanks for the input! :) I liked the left one more too, but I liked the fins on the right one, so I combined them.

I also didn't like the spiky hairs, so I got rid of them, and then I had to get rid of the fin on the left because it looked unbalanced otherwise. Frankly, I'd get rid of the top and tail fins too, but it seemed like fixing the back without the fins would be too complicated.

Making the fins warmer is a great choice! Now, I feel like my attention drifts more to the face. Removing the extra fins and spikes on the legs helps a lot too–I like the smoother look + stronger shape it creates and there's less distraction on the bottom half of the overlay.

Removing the spine would def require a bit of redrawing, especially since the fins cast a shadow. It'd require some patience and a lot of zooming-in I think hahaha, but I don't think it'd be too impossible if you'd ever want to tackle it. Anyways, this is a really clean overlay. I love your color choices and how well it all goes together. :D