If I can, I'll use a Conquest/Eagle/Falcon/Medusa/Hammerhead/Wolf depending on which is the heaviest I can grab. I usually won't use any other ships of those levels because either they're asymmetrical (I hate asymmetry in ships), they don't pack enough firepower for my tastes, or they're too slow.
The Wolf is more of a "Oh god I'm getting my butt kicked I need a better ship now" thing.
The Hammerhead is usually my first goal. Cheaper than the Medusa, and can house a Broadsword wing. It also has ballistics, which are very versatile.
The Medusa is an on/off thing. Sometimes I go for it, other times I skip it. The Hammerhead is already pretty good, the Medusa would just be icing on the cake.
Then I'll usually go for an Eagle, but if for some reason I can't ever get one, I'll likely settle for a Falcon.
Nearing the end, I'll usually go for a Conquest if I can find one.
