Thanks people, I'm still no nearer to deciding. Of all the people I've shown them to its fairly evenly split possibly slightly leaning to the dark one.
The light one is more what I had in mind but I agree it looks a little weird with the lights on. I had the idea in the daytime and thought that I would come back when it was darker for a longer exposure. I'm thinking of buying a filter kit so maybe I'll shoot it again in the day with a 10 stop ND when the lights aren't on.
I much prefer the dark one. The light is basically boring as you have to deal with a washed out sky, and a lack luster water other then the central image and reflection. In the darker photo, the sky and water have some tone variation to hold my interest. Also there are nice blacks that the lighter image just lacks.