On a twilight/night dive, i forgot to open the strobe on the camera, which was inside the housing. Luckily had also attached two sola 2000 and shot some images with both on full power. There was some processing involved, but here are two examples. Unless u have some really powerful lights, i dont believe that video lights are really an option for still images. Though for stationary and slow moving subjects they may work. Increasing the ISO would help solve this problem, albeit not completely in my opinion.
The puffer was shot 1/100 @ f 4.5 ISO 100 and the frog fish 1/50 @ f 4.5 ISO 100
I had seen a guy in Phillipines shooting with two sola’s 4000 lumen each with some nice results.
I would suggest the smaller dome for the simple reason that its easier to maneuver while in and through the cage bars. The only issue is that with a smaller dome the strobes have to be closer together than the wider dome. BUT i guess you will be taking pictures sans the strobes and manually white balance. So go with the smaller one. I have not seen a herculean difference in images with both except that the smaller dome is better for CFWA pics.