In most cases, the "G" lenses are newer designs that perform better than the older, "D" varieties (all other things being equal -- like the max aperture, etc.). They tend to have better lens coatings, better use of low dispersion, anomalous dispersion and aspherical elements, and more rounded apertures (which provide better bokeh). For use on DSLRs, the "D" lenses only have an advantage when you "freelens" or use the lens reverse-mounted or on a "dumb" tube for macro work, since there's no easy way to control the aperture on a "G" lens when it's not electrically connected to the camera.

"D" lenses, though, can be used on older, non-AF film cameras, where using manual exposure (or aperture-priority AE) means using the aperture ring -- there's no control over the aperture setting on the camera body other than what comes from the AE system in Auto, Program or shutter-priority mode.

If you have no plans to use an older Nikon film body, then the "G" lens is the way to go, particularly if the price differential is in your favour. But check the reputable reviewers before opting for "cheap for cheap's sake" -- there may be a very good reason why one particular lens is more expensive than another.