I choose the Aquatica over the Subsee for my NEX7 system because it is considerably smaller and lighter. The diopter has excellent glass and has given me sharp responses with very little CA (see hair on crab below). It's been excellent, especially used on APS-C sensor cameras. The new larger and heavier Subsee's are designed for FF, along with the Aquatica I believe, so it works great with cropped sensors. Plus, you can mount 52mm filters or lens cap to the front, something I higly recommend, as a boatman laid the rig down face up into the glaring hot Thai sun and fried my camera len's aperture in a couple of minutes from the sun's magnified and focused rays passing through the diopter. Fortunately, my 25MP NEX 7 sensor was spared. The diopter doesn't come with a cap, but any 52mm lens cap will work. Nikon makes a nice one with a strap. Now I cover the diopter before I get to the surface and hand the camera to the boat person.
I use the A+10 with my 18-55mm Sony zoom and a Nauticam swing mount that lets me use the 18mm for some mild wide angle to normal lens coverge or go to 45-55 with the Aquatica+10 for decent close macro. It's a nice versatile single dive set-up.
Some recent photos with 18-55 zoom and Aquatica +10: