Benitez coached both clubs and believes the Scudetto holders currently hold a slight edge.
He told La Gazzetta dello Sport: "What can we expect? Probably the usual Napoli-Inter clash. Right now, with two weeks to go until the transfer window closes, they seem like the more complete teams.
"Napoli have a slight advantage, based on what we know: because they won, which is fair; and because they still have (Antonio) Conte on the bench, which is bound to be a factor."
On Kevin de Bruyne at Napoli, Benitez continued: "We're dealing with a midfielder of rare intelligence. He's a man capable of making the difference. He has a commanding personality, and he'll become the undisputed leader of a team that has never lacked character, inherited from a coach who knows how to win."
And on Inter, he added: "Inter's structure is strong, their attack has international consistency. And then they've targeted future deals: (Ange-Yoan) Bonny, for example, who, behind Lautaro (Martinez) and (Marcus) Thuram, can only learn quickly."