Valeria, I'll hop in again with a few thoughts on both macro lenses and on housings.
First the macro lens. As I have said the 70-180 is my most used lens underwater due to its flexibility. And technically, at the optimal apertures, it is probably not as sharp as the new 60mm and 105mm Micro-nikkors. But in most practical shooting situations, those optimal apertures, f5.6 or wider open, do not give you adequate depth-of-field. And if you stop any of those lenses down to working apertures like f11 or even f16 to get more depth-of-field you lose some sharpness to diffraction which tends to "even" the difference between the lenses. And getting the shot, any decent shot, is far more important than such technical differences. This is where the advantage really goes over to the 70-180 UNLESS what is most important to you is subjects that are very small and where the difference between shooting at .75x and 1:1 is really important. Concerning the fact that the 70-180 isn't f2.8 for ambient light shooting, you also have to make a judgement on whether the absolute lack of depth-of-field, which you would have when you shoot a macro shot at f2.8 or f4, is going to produce a professionally acceptable image. Pehaps you might be better off upping the ISO until you can shoot at an aperture with more depth-of-field.
Second - housings. I feel that as long as a housing is of reasonable construction, the controls it has or doesn't have, plus how easily you can use those controls, is the single most important factor in choosing a housing. As I wrote, I've just bought Subal housings for my D800's, making a switch from Seacam. I changed because Subal has controls for camera buttons that Seacam does not have. These include the auto-focus on, preview, and function buttons. Subal also has a port lock which keeps a large dome port from starting to dismount accidentally. I had to add this to my previous Seacam housings. And Seacam still does not have one despite a multitude of complaints.
I shoot using TTL flash with Ikelite 161 strobes, which I think are the best strobes for TTL. Inons work reasonably well slaving off of the pop-up flash on the D800, but Inon's are powered by AA batteries that need to be changed every dive or two. And slaving off of the pop-up flash drains the camera battery much faster requiring camera battery changes which may be very inconvenient, depending on which housing you have. The Ikelite 161's have proprietary battery packs that can give you hundreds of flashes over dive after dive before they need recharging. Particularly their new Lithium battery packs.
Back to housings. On Seacam, it is almost impossible to reach the control that depresses the flash compensation button when your left hand is on the handgrip of the housing. To access this small lever you need to take the housing down from your eye and hold down the flash comp lever while simultaneously turning the front input (also the aperture control in manual mode) control dial. This is a two-handed operation and you probably need to first push the info button so that you can see what changes you are making on the camera's rear LCD panel. Then you do the two-handed gymnastics to increase or decrease the output of your TTL strobes via flash comp. By the time you've done all that, the shot may be gone. With Subal the flash comp is a push button that I can just barely reach with my right index finger with my hand on the housing's handgrip. I will modify this control to make it more easily reachable and make it possible for it to be locked down.
Please feel free to contact me directly about housings or about lenses for Nikon. Like you, I'm a full-time professional photographer. My pictures and stories been published in many of the world's best magazines. When you come up to Florida, please let me know as far in advance as you can. If I'm home, I'll do anything I can to help you.
Edited by divegypsy, 19 July 2013 - 12:30 PM.