Vertical node graphs like Houdini, Nuke or Katana tend to work for "pass the world" , whereas horizontal ones allow for more data specific passing instead.

It's just a difference of approach in what's going from one to the other. Houdini for example switches to horizontal data passing for VOPs.

I find horizontal data graphs easier to reason about at a glance, whereas vertical ones are easier to quickly prototype things.

Horizontal is just more explicit about data flow.