I've also wondered why they separated the servers out...whereas the PC is all in one client.

Benefit of one app, yes true, more player count due to more exposure (think combining classic and era). Also, adding new servers would probably be easier, rather than getting a new app approved for Zone, they could basically just update the app to add the Zone server on the list etc.

The only downside I see is that, one bad server would yield bad reviews for all servers, since they all share the same app. Maybe a chaotic tech support... bugs/glitches/updates would shared across servers.