depends on you - - - do you have the time to brush it on ?
How are your brush skills ? Have you ever painted anything before ?
How much area are you talking about ?? 10' Jon boat or 20 footer ???
Do you have a blank hull inside ? or already have flooring, carpet, seats, etc etc etc.
I have done all three.
brush when I have the time and it is small area.
roller it out on large areas, touch up with the brush.
quick n easy: Wagner Power Sprayer if you have one.
and believe it or not, I have used a pump-up garden sprayer !!!
Using latex paint, thin it down quite a bit, strain it through a fine mesh paint strainer.
Pump up and spray. Address the runs with a brush.
Seven Bucks at most hardware stores. 1-1/2 quart capacity.
If you prefer to use oil base paint, just throw it away after use.