Any cooler that makes the most cooling with the least restriction and pressure drop... so it depends on estimated boost, airflow/hp and the efficiencies of the turbo(s).. Never seen the so-percieved "big turbo lag" by going big, the opposite is more often what happens.
Assuming you have your turbocharger compressor map and a target boost pressure and massflow, then a simple 1D model using the data supplied by the core manufacturer will get you pretty close.
