Which is better: Barbie or Disney Princess?

Help! I need to buy dolls for my nieces. The dolls will be surprises so I cannot ask my nieces what they want. Which are better dolls for little girls: Barbie or Disney Princess? I deeply apologise if this post has shown up twice. I tried to post the same topic, but nothing ever showed up. That is why I am posting again. Anyways, please tell me about the best options regarding dolls as gifts: Barbie or Disney Princess!