I want more physical controls (knobs and buttons) than I have. I am not a big fan of menus. Would like DOF preview, the ability to function with older lenses. The ability to lock the focus point is important. My plan would be to keep the D5100 primary, but that could change. If I liked the operation of a D200/D300 it could become primary. I am satisfied with image quality fo my cameras. My dissatisfaction is with how they operate.