HI Paul
I know you used to be a Nikon user yourself, and myself, I used to be a canon user in them days of FILM
never had a siggy fail on me, more than likey because as your discription says, i've only ever used them underwater and not really worked them hard.
after switching to nikon a number of years ago, my 60mm & 105mm used to alarm me with motor noise as i was not used to this coming over from a 20mm USM (canon) , which well for my deaf ears, was silent.
I suppose it really all depends on budget, what your happy to spend on glass, and what you want from your final images. I remember the days when i never would have entertained the use of a ZOOM lens.
my nikon 20mm was the bee's knee's, then i moved over to digital.
I now actually find myself quite happy to use Zoomers, Strange , maybe the overall quality from the glass men has gone up. Even JB is using a 12-24mm and John was a 20mm fundamentalist.
Very funny how things change, But my words to this post would be if you have it spend it, if you dont ,then take a look at the other makes.
The internet and this list has been such an incredible resource for UWP's. We can now obtain information from those people who have first hand use of the equipment we are looking at purchasing.
So Post every and enjoy the replies.
regards
craig