A 180 will give a more even field of illumination than 150, and 150 than 135. But you can obviously
balance this out with either a custom-ground diffuser above, or by careful dodging/burning of the
corners of the image during printing (easier in b&w work than in color). It also depends on how big
you need to enlarge, combined with how tall the enlarger is. I have sucessfully used all these focal
lengths for 4x5, as well as even longer lenses. Most modern lenses by the major manufacturers will
be excellent for typical applications (Fuji, Nikkor, Schneider, Rodenstock).