Bit of both to be honest - I think a bit of geographic zoning can be helpful, but also some comparative zoology.
I've often thought that Curator of Australasian Fauna would be an interesting role.
But probably not at Chester.
I'm not a fan of hugely expensive immersive exhibits for a tiny number of species (or even just a single species). A row of enclosures for similar, but different, species suits me fine!
Another problem is that if you spend a fortune on an exhibit for Ruritanian Fleetfoot, with authentic Ruritanian architecture, boats and religious imagery ... and your Ruritanian Fleetfoots keel over and die and can't be replaced, what do you do?
The obvious. Replace them with the closely related Ruritanian Slowfoots, the public would probably never notice the difference. also they would be easier to catch, being unable to run as fast as the fleetfoots.