I had a fisheye die on my last trip and bought a nano on board. I really like the nano. It's a great focus light as long as you get the addon frosted glass.
Pro: very robust sofar, easy to charge, little maintenance, lots of double o-rings, handy bulb/oring storage inside the lamp.
Cons: expensive, little heavier, expensive, a bit too bright even on the lowest setting (I couldnt approach basket stars with it, which I could with the fisheye), expensive, doesnt come with spare bulbs which I think is quite absurd as it's so expensive.
Since Ive wanted to throw my fisheye overboard on many occasions I think the nano is a pretty decent alternative.
Cor