Put the potatoes in a large pot and add water to cover; season with salt. Bring to a boil, then reduce the heat and simmer until tender, 10 to 15 minutes. Drain and transfer to a large bowl. Add 1 tablespoon vinegar and 1/2 teaspoon salt and toss. Let cool.
Mix the mayonnaise and sour cream, the remaining 2 tablespoons vinegar and the sugar in a small bowl. Add to the potatoes along with the hard-boiled eggs, celery, chives and dill; season with salt and pepper and toss.