I know both and truly believe Javi is better than De Jong. The dutch is a very good defensive midfielder, one of those aggressive ones that tries to be everywhere every time. Javi will be on the right place always. Or almost always.
It can be my personal taste, of course, but I prefer more positional defensive midfielders like Javi, players who close gaps on defensive transitons before advancing the field to tackle the player with the ball. But of course it will depend on the team's organization.