Hmm, but going back to the armament of the Sunderland vs. Catalina:
The Short Sunderland Mks III and V (by far the most common) had 8 .303s plus an addition pair of .50 MGs (or 4 .303s) in the nose and two in the beam postion, which made it the better defended of the two planes--the turrets were a bonus. It had a reputation, among allies and axis alike, for being a very scary plane to try to take down, being able to fight off groups of Ju88s, even. The Flying Porcupine nick was well-earned..
As I said, I prefer the Cat for emotional, like-the-look-of-it reasons, but I have never seen anyone claim it was better defensively armed than the Sunderland.
By the way, there are quite a few good shots of a Cat in Tora Tora Tora, flying and on the ground.