They're very different experiences, which makes picking even harder because you can't compare them. Like apples and oranges.
Personally I would pick Spain over Brazil simply due to the safety issues and the political climate. And China is huge so if you're considering that, you need to narrow it down. A Beijing trip will be VERY different from a Shanghai one or one in Guangzhou.
The Asian and European destinations will be more of an adventure style trip whereas Bora Bora will feel more relaxing since you're at a resort. All will have some kind of wild outdoor experience to offer if that's what you're looking for.