A fish lives at the depth of 1000-2000m and another at the depth of 200-700m. Which of them would have a more developed gill system ?
200m is still pretty deep...
However, I'd give my money for the surfacers. Oxygen concentration decreases with the depth, and so abyssal fishes have very low metabolism, mainly focused on anaerobic muscles. This is also true for fishes that live in the bottom (benthic), which probably also applies for those living in a few hundred meters. If not, they will probably be active swimmers and then they will probably need bigger gills in order to maintain aerobic movement. Even if we're talking about abyssal and non-abyssal benthic species, I think the abyssal ones would probably be even more anaerobic.