I have not listened to netitehr of them but Gwen´s one is a no straight away. Few voices can make Xmas music justice. Apart from the monumental and universally appealing voices Mariah Carey or Celine Dion have (the two best selling Xmas albums ever and for a good reason) you have people like Michael Buble, even Leona Lewis and some others. But Gwen is a no. Fantasia´s is probably great. Although her voice doesn´t fit as much as those others. But she is a real talent and she always delivers for her fans.