Regarding o/b's with small fuel tanks:
I've had no EFI outboards; not yet anyway. From all reports they sound good for starting easily. Also have heard horror stories from those who did run into problem with EFI apparatus and tried to self-remedy (fix) the situation... take-it to a shop was end result, and rather expensive.
I've found using Berryman B-12 Chemtool on a regular basis added to gasoline keeps carburetor as well as other fuel line items internally free of build ups. I've yet needed to rebuild or replace an o/b carburetor - that's from 1960's to now.
Regarding inboards with larger fuel tanks:
Gasoline water build-up and Ethanol/Dinosaur fuel separations as well as critters growing in gas/diesel tanks that hold fuel for longer (six months to couple years) durations...
I've found that Soltron does the trick for keeping gasoline in good condition. Gas tests in clear bottle poured from my engines' canister filters always tell the story. As well as my engines' easy, quick start and smooth running at all rpm levels.
From what I understand Soltron works just as good in diesel fuel too.
BTW - I get Soltron from local NAPA auto store. Minimal amount of Soltron needed to be added makes it an easy application and considerably affordable fuel-safety measure for whenever adding fuel to tank.
As an aside - I don't bother to add Soltron to our 6 gal o/b tanks because their contents are gone through so quickly. And, If I were to take extended cruise on our Tolly where we were depleting, then refilling the tanks on a regular basis I would use 1/2 recommended amount of Soltron. When our 100 gal tanks are down to 1/4 level (25 gals each) I add can of Berryman B-12 Chemtool for internal fuel line cleaning. Then, when the tanks get to 1/8 level (12.5 gals) I add gasoline in what ever amount desired... full-up or otherwise! And yes - I have fuel level measuring device that gives me "exact" content level in each tank.