I think either approach could be taken. The random hordes? Yeah I can see that, literal "horde mentality" may exist in whatever state their minds are in.
But in terms of the "Blood moon", it is some kind of supernatural force that drives them into a enhanced state, and directly to where you are unprovoked. I think it would be as likely they would come from all directions as it is in one cluster. Whatever drives them to you would send zombies your way from any direction, or a random group just happens to be in the area and triggered to run your way. It would be harder to defend against, but it would add a sense of panic having to defend multiple points of contact.
Perhaps a mode or a mod down the road? ¯\_(ツ)_/¯