I'm studying in the Bachelor/Master system because Hesse (where I live) got rid of Diplom years ago, but don't you still have to do your Vordiplom before finishing your Diplom? I thought you had to reapply for your Diplom like you do for your Masters.
I think the Bachlor is getting the common degree, because it´s not easy to even get into the Master. a Diplom would be better, because i know that I will have my 5years.
That being said, like someone said before, it really doesn't matter. If you're worried about transferring later on, then the Master's program might open up more options, it might not. That really differs from university to university because in some places the transition from one system to the other has gone well, and in others... not quite so well, so it's impossible to say what's universally better. You'd probably be best off talking to the Fachbereich of the university and getting their opinions, they'll be able to give you information a lot better than we can.
EDIT: @DonaMartz, I don't know much about companies outside of the games industry, but they could never say that a job can ONLY be filled by someone with a degree from the Masters system, because that would exclude everybody who studied before that. Within the games industry, from what I've seen, they usually say "Bachelor/Masters in computer science or equivalent training", so if you say "I studied computer science for five years in Germany, here is my German diploma", everybody should understand. Germany isn't some exotic country that has no reputation within computer science (or the technology in general).