Pusher fan ?

I'm debating on a pusher fan for my rig or just buying a smaller older airboat. in all of the forum searching I've done I cannot seem to find out why the pusher fan guys have the entire fan move rather than steering fins like an airboat. I would think fins would be a much easier fabrication job.

Also, why do they get mounted soooo high? does it really matter if the wind blows onto the hood of your outboard? I would think a lower fan would trailer easier as well.