Indonesia because their unique resources upon founding a city outside the starting continent seems to be: A) a great reason to want to found colonies (I usually take other people's cities on my own continent before I look abroad) and B) lets me trade my unique resources to others that can't get them. Also the kris swordsman seems like it gets unique promotions, some being quite powerful. Their garden replacement though ... it seems like it's best used if you're inbetween three or four religion-founding civs. If that's the case, then you end up founding your own or at least getting lots of great prophets to make religious sites? I'm sure there's a neat way to use that UB, but it's too soon to tell.