D300 Color Space setting?
If you are talking about what colorspace to set in the camera, then if you shoot RAW it makes no difference, you set the colorspace in LightRoom when you export as a Jpeg or Tiff.
The only difference is that the camera includes in the metadata with the raw file a flag to say which colour space was set on the camera.
As a general rule I always say use sRGB until you know why you would want to use Adobe RGB, and have the equipment to take advantage of the wider colour gamut of Adobe RGB. sRGB simplifies the workflow and minimises potential colour problems.
I agree. With jpeg, Adobe RGB creates lots of potential problems to trap the unwary. Even with raw, I'd still set the camera to sRGB. Even though it doesn't alter the raw data, it minimises the chance that software converts the raw file to Adobe RGB when you're not expecting it.
PS - if you use Adobe RGB at any stage, then you really do need a fully colour-managed workflow (colour-managed software, calibrated/profiled monitor) or you are likely to get false colour.