Fury AI is pretty much what's used in WiH, AFAIK.
It sounds like you are trying to make a smarter opponent, independent of the bonuses and handicaps that accompany the player's choice of difficulty. In that case, you should definitely be starting with Little Devil instead of BALLS OF STEELE, because as mentioned above, BALLS OF STEELE gives AI ships bonuses that the player cannot achieve by changing the difficulty. Little Devil is just as "smart," but without the cheats.
If you're comparing to single player, go ahead and use medium, or whatever your usual difficulty level is. If comparing to multi, use insane, since that is how multi is played by necessity.
After you've made it "smarter" (or given up because it's impossible

), you'll be free to give it the crazy BALLS OF STEELE buffs to make it "harder."
Finally, if you're doing this for an actual campaign, there was a
lot more that went into making tough aces (I'm thinking specifically about "My Brother, My Enemy") than just making them more difficult to defeat. The music, their callsigns, their equipment, and intercepted messages all played a big role.