Place water in very small saucepan; sprinkle gelatin over. Let stand until gelatin softens, about 10 minutes. Combine 1/2 cup cream and 1/2 cup sugar in medium saucepan. Stir over low heat until sugar dissolves. Pour into large bowl. Whisk in 1 1/2 cups cream, then sour cream and vanilla just until mixed. Stir gelatin mixture over very low heat until gelatin dissolves; whisk into cream mixture. Place 1 berry in each of 6 Champagne flutes. Add cream mixture, dividing evenly. Chill until panna cotta sets, about 3 hours. Toss remaining berries, 1/4 cup sugar, and vinegar in bowl; spoon over parfaits.
