Depends on where you sail.
In the tropics, the ambient water is usually too warm (over 85 deg.) & water cooled is quite ineffective, energy wise. So, in the tropics you really more depend on air cooled then water-cooled adjunct.
To me, the best of all worlds is an air/water cooled, as when the water is too hot you simply turn off the pump and allow all the heat transfer by air cooling. Plus, when youre on the hard, turn off the pump and still have refrigeration.
All that stated, the 'best' is attained by 'monster' or Ultra-efficient insulation of the 'box', then your heat transfer and energy demand will be much much lower.