Heat grill or grill pan to medium-high.
In bowl, whisk together vinegar, lemon juice, chives, mustard, sugar, salt and pepper. While whisking, add oil in a thin stream.
Combine chicken and 1/4 cup of the dressing in a glass dish or resealable plastic bag.
Remove chicken from marinade and grill, turning once, for 12 minutes or until internal temperature registers 160° on an instant-read thermometer. Cool slightly.
Meanwhile, combine spinach, mango, raspberries and onion in a large bowl. Toss with remaining dressing.
Slice chicken into bite-size pieces and either toss with salad or fan over top of greens. Sprinkle salad with goat cheese and serve.
