the direct drive vs clutch is where I will throw my 2 cents.
If I were looking between those I would pick direct drive. might rob a few hp at the top, but is simpler and less to go wrong.
Generally speaking, a direct drive fan is limited to fan blade size/pitch because of the power needed to drive it. (belt slip) A clutch fan can have a much more aggressive blade profile and will move more air at the rpm it's needed.
