Nikon 50mm af-s 1.4g or Nikon 50mm af 1.4D?

Nikon 50mm af-s 1.4g or Nikon 50mm af 1.4D
The af-s 1.4g is more expensive so i assume its better?
But i'm unsure
What is the difference?

The primary difference is the AF-S "G" lens has an internal focus motor, so it will autofocus on Nikon's entry level cameras (D3xxx and D5xxx), while the AF "D" lens requires the focus motor to be in the camera body. Only the D7xxx and above cameras have these focus motors and will be able to autofocus the AF "D" version.

While using an AF "D" lens on a D3xxx or D5xxx will work, you will have to manually focus.

An AF-S "G" lens will autofocus on any Nikon DSLR.

Otherwise, there's not much difference in the lens optics.

The "G" designates the lens as one of the new generatio of Nikon lenses. What is the difference between "G" lenses and "D" lenses?

"G" lenses have the autofocus motor in the body meaning they will autofocus on all of the Nikon cameras including the entry level "DX" format cameras without in body autofoccus motors
"G" lenses do not have manual aperture rings and aperture must be set via the camera whereas on "D" lenses there's an aperture setting ring allowing manual control of aperture which can make the lens more versatile in some situations.

Aside from those differences, the 50mm 1.4G has a more robust build than the 50mm 1.4D. Acording to NIkon at the time of the release of the 50mm 1.4G, they reworked the optics as well to improve them over the previous 1.4D.

Personally I use the 50mm 1.4D and it is virtually always in my camera bag. I have not tested the 50mm 1.4G so I can't personally comment on the difference in performance of the two lenses