I have read from several sources that the f/1.4 G-series 50mm focuses more slowly than the f/1.8 G-series model does. In the link Braineack posted (
Nikon 50mm 1.4G vs 50mm 1.8G - ima|foto ) it was pretty clear that wide-open, coma was much less well-corrected in the more expensive f/1.4 model.
If there was an issue with the tests shown above, it was that there was not much emphasis on normal, real-world apertures, like f/4.5, f/4.8, and f/5.6, not anything showing how the lenses did when stopped down to say f/8 or so for deeper DOF type shots on what I would call a "
normal shooting situation". Everything in the tests was at wide-open, or at f/2, one frame at f/2.8, and yes, there was one,single intensely flared-out extremely backlighted scene that was shot at f/8 and which has 3/4 of the whole frame basically blown out to white--but the whole image was so ruined by flare it was hard to get much worthwhile out of it, excerpt that the 1.8 lens resists flare a bit better.
If it's true that the 1.4 model focuses significantly more slowly than the f/1.8 model, that could be a practical difference. I dunno...
Seems to me the f/1.8 model gives slightly better performance, optically, at wider apertures. I just do not see the value in the f/1.4 G lens for most people.