Definitely the Roc, what goods an aircraft designed to fly along side the enemy to shoot them down when the enemy are all at least 60mph faster than its top speed. I'm going to be controversial here as the aircraft is more of a symptom of what was wrong and performed wonders despite its limitations but the Fairey Swordfish should never have entered service. It was obsolete when it first flew and by the time it entered service the Americans had the all metal monoplane Devestator entering service and the Japanese had started production of the B5N Kate.
Comparing the Douglas Devastator and the Fairy Swordfish doesnt show much of a difference
Max speed, 206mph against 145mph
crusing speed with a torpedo, 128mph against 125mph
range with a torpedo, 435 miles against 525miles
service ceiling, 19,000ft against 16,500ft
climbing rate, 720 fpminute against 870 fpminute
max bombing angle, 30 degrees against vertical (but usually 70 degrees)
warload, 1x 1,900lb MkXIII torpedo or 1,000lb of bombs against 1x 1,600lb MkXII torpedo or 1,500lb of bombs or a 1,500lb mine.
crew comfort, good against wear plenty of warm clothing.
Apart from maximum speed and the Swordfish crew getting lots of bracing fresh air I cant really see much difference.