That's really up for you to decide and to test yourself.
I run an all cannon build (all DHCs and turrets), and my skill points have been distributed with that in mind.
From my initial testings of 3 volleys with 4x DHCs vs 3 volleys with 3x DHCs + 1 quant torp, unbuffed, I was doing about 7k more damage than with the latter.
But, again, it depends on how your skill points are distributed and how you play your game.
I will say that I've convinced one of my fellow fleet mates who is sub-Rear Admiral, and he thinks the all cannon build has helped him come out on top in PvP and fleet actions multiple times.
All I can say is, test it yourself and see if you notice a difference. Don't be afraid to experiment. If you want raw data numbers, turn on your combat logging and download a 3rd party program that will help sort out those numbers.