Anyway D lences has the aperture ring while G lences without the aperture ring. Personnally, I preferred with the one that has a aperture ring (e.g. 28 - 105mm D) which made a complete lence (e.g. can be use manually). But currently, I stick to my 24 - 85mm G lence as the lence has a AFS and that is a different story.
So far I have not seen a difference in flash exposure between D and non-D lenses, with or without flash. So go figure.
Barring optical quality differences, AF speed differences, build quality differences, the D and the G lens should produce similar pictures. Especially if you shoot both at their optimal apertures (e.g. f/8, but can vary with lenses).