I wouldn't shoot the 16-35mm with a 230mm dome with the Sea&Sea modifier at much less than f/10 or f/11. I will shoot the WACP 1 at f/5 and the pictures get published! Certainly, in dark gloomy conditions, the WACP will let you get shots that are simply impossible to get with a dome/lens combination. If you always shot at f/13 or above, I guess the differences are much less marked.
Some of it depends on which camera you are using it with, and I haven't really been happy generally with the 16-35mm with the D850. The resolution really shows up the optical flaws in the system.Certainly I find that I use the WACP a lot, and the 16-35mm less and less.
I love the RS13 conversions, but they are definitely a fisheye lens. I find that the 8-15mm with a 170 mm dome gives acceptable results even at pretty large apertures. I think for some things like GWS from a shark cage, when a very open aperture will give strobes a better reach, the RS is an amazing tool, but it is a different one to the WACP (either version).
WACP-1 is around 1.4 kg heavier than a 230mm dome, extension and 16-35mm lens. Although this is significant, in the big scheme of things, this is easily managed for travel. Both are heavy solutions!
1/160@f/5, ISO400
Nikon D850, Nikkor 28-70 f/3.5-4.5, Nauticam WACP, Seacam Seaflash 60 strobes