The 14-24 is a computer designed lens (the prime may not; I'll check) and additionally benefits from likely better glass and nano coating. It has been considered the best wide angle zoom ever by advanced amateurs and professionals. So much that Canon photographers are using it with a mount adapter. It would be great to have another pair of shots from a leveled tripod.
I've done critical comparisons of these two lenses a few times. Besides the 14mm having much worse vignetting it also has much worse linear distortion. On a full frame camera the 14mm is not a good lens to use indoors where the sides of a room are near the edges and from about 1/3rd of the way from the edge. It was fine when I was using DX bodies.
If you don't mind focusing manually, there is a reasonably-priced alternative from the third-party makers. It's variously badged Samyang, Rokinon et al and has been discussed in our MF Lenses Forum here.
The older 14/f2.8 AFD is not a particularly retrofocus design. In practical terms, that means that light arrives at the film plane at fairly steep angles. On film, that makes no difference - a film grain reacts to light hitting it, and does not care what angle the light came from. Because digital sensors are sitting at the bottom of little "light wells," it is much more important that light arrive close to perpendicular to the sensor plane. The 14-24 does this as it was obviously designed with digital sensors clearly in mind. The 14/f2.8 AFD was designed in the mid-to-late 90s, before digital sensors took good hold.
_____ Brian... a bicoastal Nikonian and Team Member
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