Both of these kind of sound like a nightmare.
I would say benefits to 18 networks is that you have alot more control, but its going to be harder to manage alerts, support, etc.
1 network seems also bad from the support troubleshooting where they are and such
I would say there is a mix between the 2 that would work. A different way to create 2 or more networks Like North or South or Floor 1 and Floor 2 or maybe 100 and 200, 300 rooms.