Seven-times world champion Hendry believes Trump in top gear would win a world final "18-7 or 18-8" if the pair met at the peak of their powers, but added that his old rival's "granite" safety game would give him a chance.
Three-times World Championship semi-finalist McManus points out that it would not be a foregone conclusion because of six-times world champion Davis' ability to starve his opponents of chances.
"It's tough. When you discuss different eras, you have to remember this: the day that Davis won his world titles, all the days between now and then hadn't happened yet," said 1994 Masters winner McManus on Instagram.
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"He didn't know about Judd. He was playing the guy in the other chair.
"You've got to take that into account. I only played 'The Nugget' in the nineties, and I thought he was an unbelievable player."
Trump produced the greatest performance in a world final with an 18-9 win over John Higgins in the 2019 final, a match that saw him make seven century breaks.
While Hendry feels Trump will carry snooker to a new level, he agreed with McManus that Davis - Crucible winner in 1981, 1983, 1984, 1987, 1988 and 1989 - was a fearsome competitor in his pomp.
"There was time when you wondered: 'How could you beat him?'," said Hendry.
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"I think Judd is possibly going to take the game to a new level. Judd would probably beat him, but I'd be interested to see.
"Judd would probably beat him 18-7 or 18-8. Something like that."
McManus recalled the UK Championship final in 1990 when Hendry edged Davis 16-15 in one of the sport's all-time classic clashes at Preston's Guild Hall.
"The famous UK final between you and him in 1990. I know how well you were playing. He was playing good, wasn't he?," said McManus.
"The other thing you have to say is that Judd would need to play well to win otherwise 'The Nugget' would get him.
"Davis was an unbelievable player. I played him in my first final (Asian Open in 1992) in Bangkok. I never missed a shot, I played awesome, one of the best matches I've ever played.
"He beat me 9-3 and I was over the moon with myself."