I think that both designs will appeal to different types of individuals. I prefer the brighter colors and open feeling I get from the spacious layout of the balanced text on a bright background. I have rarely seen a dark background site that I could stay in very long without eye strain because of the poor contrast between the font colors and the background. I would suggest that you possibly use a subtle pale or very light background (slightly darker than pure white). This would alleviate eye strain and still provide maximum contrast for the text.
My opinion only, but listen to your wife.