That isn't a string to Navas' bow, both did virtually nothing. Might as well compare the contributions of Foden and Diaz to City's first team last year. Only difference is Silva was one of Spain's best players when they won Euro 2008 and 2012, Navas never did anything of note for Spain.
Only reason Navas got into the Spain squad at all is because despite the quality Spain had in virtually every position in that era, the wide areas were the one area where they lacked top class players. Silva got shoehorned into the team in wide positions a lot at the time because of it.