The highly rated duo are attracting interest from leading sides across Europe, with Goal revealing that Premier League champions City are ready to splash the cash.
Big-money deals are considered to be only a matter of time, with a scramble for two sought-after signatures expected to be sparked at some stage.
De Boer hopes La Liga giants will emerge victorious in those transfer battles, with the Dutchman told Esports COPE: “I advise them to sign for Barcelona, or if not, for Pep [Guardiola’s] Manchester City.
“Ajax’s style is the same as Barca’s, they could adapt quickly. I would also advise them to go to Barcelona because the club is in my heart.”
Both Barca and City boast the financial muscle required to do a double deal, but it could come down to who offers the better personal terms.
De Boer hopes that will not be the case, adding: “One million more or less doesn’t matter.
“The important thing is that they go to a team that fits their style. They have a lot of quality and there are many clubs interested.”
De Boer also believes that Barca have the greater need to land De Jong and De Ligt, with a freshening up of an ageing squad in Catalunya required if they are to avoid going the same way as Bundesliga champions Bayern Munich.
A man who took in two spells with Ajax and one at Camp Nou during his playing days added: “Barca have to renew their team in the coming years because if they don’t they will have problems like Bayern.
“It is better to sign young players now and to get them ready for when they have to start games.”