25/34 1. Fan blade shape. Flat plywood blades suck. A good fan will have blades that are shaped and sculpted, changing profile the further out from the hub you go. They look more like airplane propeller shapes, for the same reasons airplanes want efficient blade shapes. Better-shaped blades will also generally mean fewer blades - rather than 4 or 5 flat-paddle blades, a good fan will come with 3, or even just 2, sculpted blades. The 2-blade ones really do look like an airplane propeller.