Brown has performed a creditable job at the KC Stadium since taking charge almost three years ago and led the club into the Premier League before retaining Hull's top-flight status last season.
However, the Tigers have won just three of their last 32 games in the league and the pressure is starting to mount on Brown.
A 0-0 draw at home to fellow strugglers Portsmouth on Saturday left Hull in the relegation zone as the memory of last season's flying start slowly evaporates.
Duffen, though, feels Brown is being unfairly criticised this season and has no qualms in comparing the manager to Benitez, who has also seen his future at Anfield questioned recently.
"If you look at Phil's squad and what he will do with it this season compared to Rafa, you'll find Phil will come out top in terms of adding value to players," said Duffen in The Sun.
"We were written off by everybody last year and told we were going to redefine the expression 'doing a Derby', but we broke all records for a newly-promoted side.
"People use that as a stick to beat Phil with because he over-achieved so much last year."