I always felt the Sunderland made a great contribution, especially the fact they were so big and hard to miss, as far as U-boat gunners went...
It was a shame they weren't more heavily armed, like the Jap 'Emily' [which was a Jap version of the Short aircraft], where even .50 cals like the Catalinas had couldn't have been as effective as 20mm's...
Unfortunately, the bigger the aircraft, the larger the crew-loss if they were shot down...but Sunderlands, and Catalinas overall service was pretty major, the rescue work they did especially, but I take my hat off to the crews, as in reading of their conflicts, the courage they had to take on heavily-armed subs was extaordinary.....they at least could alight on the water if emergency warranted it, something the Wellington, Whitley, Halifax, Liberator Fortesses couldn't do, along with the smaller anti-sub aircraft...
But all these aircraft battled-on, gradually reducing the U-boats from predatory wolves to hunted dogs. The Hunter-killer packs of Corvettes, Frigates and Destroyers certainly played a role here too, particuarly in the convoys, the co-operative venture of these ships and aircraft was the winning formula.....
I feel the Avenger was significant in the PTO, as was the Catalina, and in the ETO, MTO also, as both Allies used them...As I understand it, the Swordfish is really in a class of it's own, the only biplane through the War, and the awesome courage and skill of Taranto, but it's replacement, the Albacore, was useful [although not liked by it's crews], but the Barracuda, for all it's wonky undercarriage, gave good service in the last two years of the War, particuarly in attempted sinkings of the Tirpitz [finally sorted-out by 617 Sqn. Lancasters].......