I'm not going to go very deep in contrasting the two, but I'm just warning you in advance that this review pertains to the English version. I chose to watch it because I somewhat feel it's the original in certain respects. The reason I've only watched one version is that I didn't feel I could write an effective review with two scripts crammed into my head. So with that being said, please keep in mind that the Japanese version could very well be better, or it could be worse, but this review is only based on the English version. First off it's almost impossible not to talk about Sin's origin.
Sin is based off a PC that has a small cult following, but was never terribly successful.
Regardless, ADV choose it as their first anime project. Sin's story and characters were mostly conceived in the US, though the Japanese had a fair amount of input. I feel the entire concept of Sin's creation is very interesting and commendable, but in the end it's what I see in front of my eyes that counts. Despite where the video game came from, video game to anime ports are usually a miss. Yet every now and then there is a hit.