What are the advantages of a lens having a Fixed Maximum Aperture? Previous answers have indicated that "pros tend to want constant apertures in zoom lenses".
While in general lenses with a fixed maximum aperture tend to be more expensive and thus have a larger aperture, this is not always the case. To take a random example, the Canon 10-22 has a variable maximum aperture from f/3.5 - 4.5, while the Tokina 12-24 has a constant maximum aperture of f/4. In cases such as these, is there a reason to prefer a fixed maximum aperture?