It depends on your needs. Clearly, prime lenses generally are better lenses; less distortion, finer resolution. The advantage of the 10-18 is that it nicely fills the lower gap of the 16-50 or 16-70. Since focal length is a logarithmic function, 10-18 is about the same range as covered by 16-50 so they go together nicely. I had compared the output of the zoom to the prime wa lenses in prints and can't tell the difference. Maybe if you're making 24x32 enlargements it would showup. I am more concerned with the convenience of carrying fewer lenses and have stuck with zooms.