Yeah I'm gonna have to go with NA here. Grasslands is arguably more usable by worldwide standards and is more diverse, but to answer the actual question, NA is by far one of the best representations of its theme we've had to date. It represents ecosystems all across the continent, and nearly every animal pick ranges from common to essential, with the only two that don't (beaver and moose), being far too iconic to leave out. Honestly its the only animal pack that doesn't have at least one dud of a habitat animal (at least to me, I could maybe understand including Grasslands in that too though), everything here is super worthwhile. Pretty much its only major flaw is the missed opportunity to represent at least one of the many bird niches NA is still missing.