Well, you are going to have to look at what you are using it for. When it comes to mat runs, I suggest getting a War Galleon and upgrading it to Cargo Tier III. This is a very short process, and it will give you a strong ship with 28 slots of cargo. If you want to do loot runs, go for the War Sloop. It is small, fast, and can hit tiny ships without an issue. When it happens to be the question of Frigate or Brig, I say that it all depends on what you want it to look like. If you want a classic pirate ship, go for the brig. That's just my two cents.