Brightness and Contrast Setthings

If I import images to LRb4 with a linear tone curve set, the brightness level is set to 50 and the blacks level is set to 5. If zero'd is chosen from the presets, as you would expect, the brightness and blacks sliders are both set to zero. I'm wondering which is a true starting point or whether there is no such thing with a RAW file? Will one or the other be better for avoiding shadow noise as much as possible when adjustments are made? I thought I read on Adobe's introduction to beta4 that the brightness slider may eventually go away. If it does, which one of these presets will we be left with?