Using a food processor or a hand mixer, combine the cream cheese, sour cream, powdered sugar, and vanilla extract. Blend until smooth and creamy, about 90 seconds.
Place the cream cheese mixture and the grapes in a large mixing bowl and gently mix until evenly coated. Cover and refrigerate for at least 1 hour to allow the flavors to meld.
Just before serving, sprinkle with crushed pecans and brown sugar for added crunch and sweetness.