You're hittin' a topic near and dear to me... living in the northwest meant smokers in every backyard during salmon season!
I have owned the Luhr Jensen Little Chief and Big Chief and have had great results with them. The BC can handle whole fillets that are aethetically a thing of beauty when serving. The LC requires that the fillets are cut up and placed on the small square racks. I like the big one better, it is just that much easier to user as well.
A few tips:
Fresh fish varies widely in condition and brining can have a range of effects on the meat. It can be too salty or not cured enough, even in the same batch. Frozen fish is consistent (consistently worse to eat, but...) to brine and even though it's not as good to eat it is easier to smoke. It all seems to come out the same. If you are sure of the condition of the meat and the relative brine times, then fresh is superior of course.
Letting the pellicle form over several hours is the key to holding the moisture inside.
The electric heating element is about the only thing that can go wrong with these units. Eventually you may need to replace it. The rest of it is indestructible.
I prefer applewood chips for fish, it comes mixed with alder. Hickory is strong for fish, but bluefish might be gamey enough to take it.
Ambient temperatures make all the difference in the results and smoke duration. A long cold smoke makes the meat rubbery and the pellicle leathery, I like outdoor temps that permit a 6 hour duration in these units. I've had 4 hour smokings and 12 hours smokings, one too hard smoked and the other too stiff.
MMMMMM I am jonesin' for a nice slab of applewood smoked wild sockeye!