Re: What is the EVGA External Exhaust for the GTX 460?
If the ambient temp of your case is pretty cool and has plenty fans/airflow I'd go with the non-external exhaust since it's quieter. It's cases that have few fans and little airflow that may benefit the most from the external exhaust.
The external exhaust cards typically have those squirrel cage fans that have to spin very fast to get good airflow and they can make a lot of noise once they get going.
The other card has a standard fan that can typically move a lot of air without making too much noise. But they mostly circulate the air inside the case and don't vent much of it out.