Tough decision. I've had both, but both rooms also had at least one full-size window to look out. When both kids were home (not the boomerang time they were both home - they leave, but they boomerang back) I loved the sewing room in the basement, as we had a split entry house with full size windows in the basement. I could "escape" there and quilt by myself and pretend I was all alone in my world. I had office and sewingroom together once - didn't work, I couldn't relax to sew when I saw my work sitting there on the desk and vice-versa. If stairs are a problem - go with what is best for you. Like someone suggested, you could put a machine down there for a while and do a trial run. Good luck.