Another thing to pay attention to is the pitch. You want as much of that as you can get. Flat fans don't draw enough air.
FWIW I went on a search to correct my factory sized 4% underdrive pulley setup and found a "high volume" 1:1 setup at CVF with the difference being the waterpump pulley. I replaced that and my fan at the same time so I can't say which one fixed it, or if they both helped a little bit, but my car doesn't run hot now. (I also have a flow kooler and a Cold Case radiator - those didn't help until I changed the pulley and fan.)