What happens on a hot day
A condenser and a dry cooler reject their heat into the outside air. As that air warms, the heat that can be rejected falls: on a condenser the condensing pressure rises, the compressor draws more energy and the capacity drops. On a dry cooler the outlet water temperature climbs above target and the process falters.
What adiabatic pre-cooling does
The air entering the coil is wetted before it gets there: passed through a honeycomb pad, sprayed onto a mesh or misted. Evaporating water draws heat from the air; the air enters the coil markedly cooler than its dry bulb temperature. The unit behaves as though it were running on a cooler day.
The gain is proportional to the difference between the region's dry and wet bulb temperatures. It is large in a dry climate and more limited in a humid one — which is why the decision is taken by looking at the site's climate data.
What it asks in return
Water. And that the quality of the water is managed: if hardness, scaling and hygiene are neglected, the system both loses its efficiency and generates a maintenance burden. That is why adiabatic systems are usually set up to cut in above a given ambient temperature rather than to run continuously.
The alternative: choosing big from the start
You can reach the same result by sizing the unit for the hottest day and running with excess capacity for the rest of the year. Which is right depends on the number of those hot days, on the space constraint and on the trade-off between first investment and running cost. We can calculate both and put them side by side.