I like to cut mine into thin strips before I put them on the smoker.
I actually cut them into strips before I ever marinade them. The thought process behind this is it creates a larger surface area for the fish to absorb the marinade. Also it cuts down on the cooking time and allows you to cook all the pieces to be done the same. (The outsides are done while the inside still juicy like with filets.)
Also, this allows you to pull pieces off the smoker after they're done and eat then.
This is a personal preference, but I have done them both ways.