I don't think there is any question that a wide angle lens, under a dome will be wider than thru a flat port. What is not so clear is how much wide angle is enough.
For the most part, if one wants to do wide angle images, an interchangeable lens camera will do a better job. And with the advent of the evil camera's, the price to do so has come way down... ok, still silly expensive, but far better than it used to be.
However, if on is just doing an occasional wide angle, or one does not need really wide angle....then a flat port with the LX-5, shooting 16 x 9 and processing with any software other than silky pix is reasonable...roughly what anyone would get putting a 28mm lens under a dome.
And corner softness with wide angle lens is a very normal thing... something I suspect would happen even if the lens is under a dome, unless the dome is made to exactly match the 24mm curve.
They typically don't make domes for the high end point and shoots because they usually come with a 28mm... the odd man out in this is the LX-5....but it is all by itself in that regard.
i have the Pany 7-14mm zoom, and the 7mm (14mm equiv) is silly wide. Great to get that passing whale shark, but everything else looks really, really tiny, including people. And unless the water is clear of chucky stuff, lighting an image with that wide of an angle almost guarantees backscatter.
Note: Although, in clear water, with a huge animal, it is very impressive.
While I have several wide angle wet lens, they don't get used that often in the conditions I dive in, but the LX -5, at 24mm does get used.
