Exhaust fan static pressure or airflow?

As nostall said, an airflow fan would be preferable.

Generally speaking, an airflow (AF) fan functions the best when mounted as an intake or exhaust. They are designed to provide the most airflow through an area that has little to no air-flow restriction.

If you happen to be mounting a radiator from your CPU or GPU to your exhaust fan grill, then a static pressure fan (SPF) would work more effectively.

I hope I helped. Have a great day!