I bought the 16mm Nikkor but was disapponted to find it did not focus closely enough so traded it for the Sigma 15mm.
I like to grab the moment and went from zooming with the Tokina on DX to cropping the Sigma on FX because I find it is the quality of the water one shoots through that is the limiting factor. With fast moving subjects one can get the long shot and the extreme close-up wide-angle with merely a reaction to the shutter control.
Here are two shots taken within moments of each other that adequately demonstrates the advantage of NOT having to fiddle with an extra (zoom) control.
Great Hammerheads move quickly. The first is a 20MP crop while the second is the full 36MP frame
As for the coruption you mention, Aussiebyron, regarding reviews and advertising revenue, that may well be true of some diving magazines but they soon go out of business!