Radiator capacity is always a big player. That being said, it is better to go wider when possible than adding additional depth.
Wider radiators expose more frontal area to air flow, assuming it isn't blocked by a tight core support.

Adding depth to a radiator is less effective. Air passing through the first core picks up heat. That means the second core is getting hit with hot air and can't transfer as much heat. The third core adds minor fluid capacity but gets blown on by slower moving air that has already been heated twice and is really turbulent. That is not a recipe for success.

Yes, additional cores help but to a limited degree.