Most of the time, learn. I do like a healthy debate though, but the goal isn't to win. Rather, the goal is to pitch one side of an argument and hope that you can learn from your devil's advocate on the other side.
I love to keep learning, this means not simply agreeing but often challenging an assumption and evaluating the reasons for it. Confirmation bias is the worst thing you can have and only engaging in debate to win definitely lets hubris creep in