Suppose there is a preference in most cases. Me, I have always been a sub
driver...but I do enjoy the surface elements now and again. In past games
I have seen people specialize...a very small number were ALMOST equally
proficient as sub or surface.
So if sub driver, I recommend finishing ALL the sub patrols and campaigns.
And going to say level 5 or so in surface. The reverse if you are a surface
dude. Good reason for understanding surface if you are a sub capt is that
you have to understand their strenghs and limitations to really excel. Reverse true as well.
Now if you are ambidextrous, and like bobbing under the water and up again, finish em all. I got stuck on trying to finish 4 subs with a PT boat
in 4 mins or so.
Good luck. Hope to see ya on the water