Damanpersonally fixed for frags - max damage. also - if you want pacifier frags they only come in fixed variant. i find them effective against med and larger ships - smaller ones not so much. double shot frags are one of my favorite weapons.
i only use the turrets on the big ships - to catch those flying over you in the face unexpectedly
the difference between a stock class 2 gimaballed or turrent (143 vs 179) is not that big...and cosidering how close you need to be, chaff won't be a problem, i would go for gimballed....hmm or still for the fixed?