We have hard flooring in the hall, as it is a high traffic area. The kitchen and dining room also have hard floors, with a large rug in the DR, and the sitting room, stairs/landing and bedrooms have carpet.
Whether you go for light or dark depends entirely on what you prefer. Both will be easy to clean, so you don't need to worry about light showing marks more than dark. Which would go better with your furniture?
We went with mid-colour wood in the hallway/dining room and the beige/cream carpet I mentioned upthread on the stairs and landing. I like it, but that doesn't mean you would. I know what you mean about it being difficult - it's a big expense and you'll have to live with your decision for a long time. I'm sure it will be lovely, whatever you decide, as you are choosing both areas at the same time, rather than matching one with the other.