thats a tough one, i personally would go carpet, definately a hard wearing dark colour. Look into the cheaper of the solution dyed nylons as they are apparently stain proof to a certain degree. Polished floors look great and are easy to maintain. However they do scratch easy and i suppose that can be classed as wear and tear on a bond. Whereas a big stain on the carpet or a tear wouldn't be. Also getting floorboards sanded and polished can make for alot of cleaning..eg windows,sills, walls.
We had polished floor boards through one of our old houses and we got a burn about 30cm in diameter in it. They had to redo the whole house, they can't just sand back and polish one section to fix it.
gl