The only time I use either is when I winterize my boat, and then I have always used stabil. I have never felt a need to add anything to the gas tank during the fishing season. Of course, I use my boat 5-7 days a week, and gas it up several times a week, from the middle of April till mid October also. I often run my tank down to near totally empty. I doubt much moisture ever builds up in the tank because I’m probably burning it for with all my use.
That all being said, I need to add that I run a Mercury EFI, which maybe is not as tempermental as many of the DI’s, 4 strokes, Opti’s, E-Tecs, etc…. I guess I’ll find out first hand after this coming season when I get into my next rig, since the EFI will not be available any more.