The pair go head-to-head at Wembley on Monday when the two South Yorkshire rivals clash in the third tier’s winner-takes-all season finale.
Barnsley edged past Bolton 1-0 on aggregate in their semi-final, while Wednesday overcame the biggest first-leg deficit in play-off history before beating Peterborough on penalties.
Moore silenced the Owls fans who had called for him to be sacked after his side’s 4-0 first-leg defeat appeared to have left them dead and buried and Duff paid tribute to his rival manager.
Duff said: “Darren deserves loads of credit because one thing he’s done the whole season, when weirdly there’s been a bit of noise about him when they got 96 points this season, is keep his counsel because he’s a good fella.
“First and foremost, he’s a good fella. He’s obviously a football man, he’s been around it a long, long time.
“I don’t know what he’s like as a manager in terms of day-to-day stuff, but you take people as you find them and we’ve beaten them twice and he’s been humble, he’s taken it.
“He says ‘fair play to you’ and shakes your hand. No excuses afterwards that some managers come out with. He said ‘better team won’ and I think that goes a long way just as a human being.”
Barnsley completed the league double over the Owls this season for the first time since 2009, winning 2-0 at Hillsborough in September and 4-2 at Oakwell in March.
But they finished 10 points adrift of their local rivals in the table, with the Owls’ 96-point tally more than any other side not to finish in the top two of any league in English football’s history.
That did not stop the vitriol that came Moore’s way after his side’s 4-0 semi-final first-leg defeat at Peterborough.
Some fans called for his head before the return leg, while Wednesday were forced to issue a statement condemning a racist message directed at Moore on social media.
“It shows you the emotional state people can get into,” Duff said. “Darren’s a good manager, full stop.
“Was he a terrible manager when they got beaten 4-0? No. And he’s become an even better manager now because of the belief he gave them.
“Things he said in interviews and in the dressing room, things he showed the players. Good management. He managed to get the best out of it.”
Barnsley finished fourth in the table, one place below Wednesday, and their 86-point haul would have been enough for automatic promotion in three of the last 10 seasons.