Good research JollyRoger,
From my experience; The biggest benefit any liability policy can offer you is defense costs!
And you want to make sure they are unlimited and not concurrent with the insurance policy limits. What that means is that the Insurance Company will pay for all your defense costs (which can be astronomical) and the cost doesn't reduce the coverage of your insurance limits.
"God and the Soldier we adore, in time of trouble but not before. When the danger's past and the wrong been righted, God is forgotten and the Soldier slighted."