Although it depends on personality rather than countries, I prefer bun bun....
Reasons:
1. in general more smart than yan yan -> this advantage is particularly suitable for taking care of baby/children
2. English is much much better than yan yan and this can improve the baby/child's English with their daily communication (yan yan may know some Cantonese but incorrect accent of Cantonese -> which may pass on the incorrect accent to the baby/child)
3. because of religion (just my personal opinion).....yan yan's religion is quite violent....and most of the child abuse I saw/heard is yan yan......I saw in the park nearby, some yan yan beat the child....