I always thought that liquid cool was quieter and cooler...
This issue has more dimensions than that.
In both types of cooling, one source of noise is the transfer of heat from the heatsink / radiator to the ambient air. In both instances you have a fan pushing air into a heatsink / radiator and this makes noise. All thinks equal a water radiator is almost certain to make more noise than a simple heatsink. They both use fins to transfer the heat, but water-to-air radiators tend to be more restrictive to airflow, presenting more impedance to the airflow, therefore making more noise.
Water coolers also have an additional source of noise. The heat pipes of an air cooler do not make any noise. The water pump of a liquid cooler is an additional source of noise.
That being said, an air cooled video card is likely to be your greatest source of noise... and heat. So if you are able to cool it with a liquid cooler, that is likely going to be the lowest overall noise cooling solution for your application... But even then, you want to pick the right water cooling components to make sure they are quiet ones. I am not a water cooling person, but my understanding is that there are substantial differences in the sound performance of different water cooling components.