I think that BD and DD are actually quite different - and I have a hard time comparing them somehow. <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
I really liked the amount of freedom you had in DD - I so far tend to get stuck in BD every now and then, and when that happens I can't just go somewhere else and try again later because the storyline of BD is much more linear then the one of DD. I am missing this freedom a bit in BD.
Some of the quests in BD are easier to solve than in DD, and, at least in my opinion, there are more logical clues to the solution of a certain problem in BD. (This, of course, does not apply to all side-quests). <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
I personally prefer the interface of DD, but it is certainly a pro to be able to control more than one character at the same time.
BD, though, certainly is a good game (especially after installing the latest patch, hehe) and I do not regret buying it at all. I personally like DD better, though, maybe because DD perfectly surprised me and my expectations for BD were explicitely high. <img src="/ubbthreads/images/graemlins/wave.gif" alt="" />