Well,
Drew:
I am full support your idea to offer distribution for the winning films. However, I feel, that the other argument - marketing - can be a very effective one also in the case of the videos. For example if I participated in a good divetrip and I was satisfied with the liveaboard ship and the crew I can put the name of the ship or the dive-base in the credits. For example, if I will plan a trip to Malpelo, I will first begin the negotiations with the Sea Hunter, since I saw them in Shawn's film, distributed via the DiveFilm HD podcast. Or, to visit Guadelope I try to find a place on the Horizont, as I saw it in Mary Lynn's film etc.
Steve
As you wrote, I feel also unfair this difference. 
I am not familiar with the rules of procedures in case of the stills, but I think there is no info about the ship or other advertizers/sponsors when a still became a front cover of a big magazine. I guess the gear (taken by Nikon D200 in Subal housing, f8 etc) and the location appear in the title of the picture.
I think, concerning the categoires, the big and mainly film festivals has several video categories - in Antibes, Moscow, Belgrade or in Turkey you can find quite good distinction between the various categories.
My favorite competetion now is the next SanDiskRedSea in Eilat, since they have a video category, and the prize is 7500 US. 
Back to magazines: they could attach a DVD to the magazin, containing the best films of a show. I think the only - real - problem is the rights of the soundtrack, since the magazine is sold for some money, and maybe in this case the music rights fell into the commercial category which can be more expensive, if ever paid to the author or publisher...
Jules