. . . I like the solidity of a lens with more blades and the nice round aperture, but that said, the optical design is a more important factor in the rendering of the out of focus portion of the image, and a lens with fewer blades stops down faster, reducing shutter lag.
I agree. My Super-Angulon f/3.4 21mm in Leica M mount has four blades, and delivers Leica quality images.