For the kinds of institutions that you applied to, 10-12 hours for 6-7 days a week is probably on the lower side in terms of average workdays in "wet" chemistry labs from my experience and observation (having worked in a synthetic inorganic lab at one of the institutions you applied to as well as doing my undergrad research in a synthetic inorganic/catalysis lab at east coast university). In organic chemistry at these top institutions, the average is probably closer to 14-16 hrs. For synthetic inorganic, the average might be slightly less, but that varies with group and advisor. I would counsel against choosing a sub-discipline based upon the work week; do what you love and then it wont matter. But my bias is for inorganic! For me, its just more fun-I love synthesizing metal complexes and working with inorganic spectroscopic techniques, I love doing detailed mechanistic studies, etc....