duplex: 10mbit full vs. 100mbit half

Just wondering if anyone has any input as to what setting I’d see better performance with in a firewall application. We’re experiencing issues when running at 100mbit full, the network card in the firewall doesn’t play well with the switch its connected to at that speed. The question we have now, is which setting are we going to see better performance with, 10mbit full duplex, or 100mbit half duplex? Any input would be appreciated. Thanks!