Disclaimer, this grossly unscientific "test" is purely a backyard comparison of two lenses on the one body.
The images were all processed from NEF to JPEG with the same picture control parameters.
Nikon 14-24 compared to Tokina 16-28
Nikon at 14 and then 24 mm
Tokina at 16 and then 28mm
Here is where it gets interesting, first the Tokina at 16mm and then the Nikon at an indicated 16mm
Then the Nikon at varying apertures
Then the Tokina at the same apertures.