I always advocate using Random companions, or at least your First Mate setting, so that you can see how each of your crew will do against various enemies. Why take others' advice rather than see what works for you, your playstyle and your crew as YOU have trained them up?
One player's Bonnie Anne, with Overwatch and Burst Fire will be different than another player's if she has Double Tap and Quick Draw trained. Someone else saying their El Toro is no good shouldn't make you dump him to the end of the list and put him on Pet Wrangling if your training of him has prepared him for ranged attackers.
To be flexible and patient is the best way to learn about your crew, and making your own decisions will give you more satisfaction when you win.
Fan, Sarah, and El Toro. It's best to use all melee companions so you can hide and attack within a few rounds. Also these companions are really great and I'd say the best swashbuckler companions. It's also best to use companions that boost to the same thing as you.