Hi, I have been using the 20170216*** file that is just the original T1 converted to nifti format. The co20*** file is the same T1 but cropped and adjusted because the excess air surrounding the head as well as the neck have been removed. The o20*** is, I think, the re-oriented image. However, I do not know how it works but when I check this file it is always left-right flipped, so I do not use it at all.

Check this out http://www.cabiatl.com/mricro/mricron/dcm2nii.html, "Reorienting to canonical space" section.