In terms of differences. Your version's eyes are different from the original-- I'd say your's eyes are better. The angle of both sprites differ slightly: your version's right arm is more visible and to the side than the original. The color choice on your version is weak compared to the som sprite, as it as more contrast between the highlights and shadows...I think you should highlight the metal on your's more. Also, if you want to get technical, the version you made has a wider head....but that said, I prefer the hair on yours over the som one.
In terms of ethics. Only you truly know the truth to the sprite, and if it's as you say it is, more power to you (make a lot of people look like jerks). But if you take personal offence to the way you've been "attacked" or w/e, you should try to take it a bit more lightly; this is a critique forum, and it's our job here to jump and point things out. I personally don't have anything against emulation of style (you could argue that all art is theft), and I feel that there's no better way to learn than copying somebody of higher skill than you, but perhaps with your next pieces, you could experiment and try to discover your own style.