Overall I think the show in general regardless of which version we're discussing is the most unique and creative series I have ever seen. I like that for once Vampires and werewolves are shown able to get along and even be friends, and their ability to converse with the dead is also a new twist from what I have seen anyway. All the storyline comparison is starting to get on my nerves actually, why is it such a big deal? I believe that even in the first season the US is doing a terrific job of taking it in their own direction. The presented the first season story lines in significantly different ways and even left some of it untouched, like the ghost character wanting to be the perfect wife and doing all this stuff like cooking and setting out his clothes at his place. In the second season and probably on they completely left the British storyline and when in their own direction.
I find in what I have seen so far in both versions that you can feel more drama in the US version, that the US characters seem to go through a lot more which tests the boundary line between who they are and who they want to be. The supernatural atmosphere is also stronger, Aidan is lot more frozen in his birth era than Mitchell and the ghost more separated from the earth. The fact that Annie can touch and be so easily seen as though alive makes no sense to me. The werewolf design in the US is also a brilliant combination of wolf like facial features and a human body figure, as opposed to the British Halloween costumes. I enjoy the British characters and adaption though just the same despite that the US characters capture me more, Aidan in particular. Sam Witwer is probably the first actor to ever make me feel so strongly for a character. Aidan's reaction to Bernie's death for example just melts me.
I look at each version as an individual personally as I do with any adaption. Comparing just sets one up for disappointment. I have got to say though if they kill off Adian like they just killed off Mitchell in the British version at the end of season three I am going to be pissed and may lose my will to watch.