i would stay with the dunk since it has more sailors slots and its more maneuvrable which mean u can get out faster.

I stayed in mine all the way up to nelly.

Stay in the dunker if you have it.

It's a PBB so it's pretty damage resistant and earns extra exp over normal BBs. 

And repulse/Queeny have one of the longest BB3 range at bb2 level.

Are you looking for leeching/ranging/rushing/linefighting?
Depending on what you want, the answer depends on it.