Originally posted by Big G It's not just about the resolving power of the lens, but the whopping gaps in the Pentax lens line up not to mention well-documented SDM problems and noisy screw driven models is what gives Canon and Nikon the edge.
Yes, there are gaps in Pentax lens lineup, but it's a bit of an exaggeration to call them "whopping." Many of these gaps are in the very expensive lenses, such as the fast wide angles, the supertelephotos, and tilt-shit lens, most of which cost more than Pentax's most expensive lenses. When you throw in third party alternatives and used glass, the gaps close even more.
The SDM problems, however regrettable, have nothing to do with the quality of the optics in Pentax lenses. As for "noisy" screw drives, well, there are both costs and benefits associated with having focusing motors in lenses. On the internet some people are warning against purchasing the Canon 200mm f1.8 lens because Canon has run out of focusing motors for this lens and if your motor breaks down (and they do eventually), you can't get it replaced. The "noisy" screwdrive lenses are likely to have a longer lifespan than silent motorized glass. Ten, fifteen years from now we may find quite a few manual focus Canon and Nikon AF-S lens being offered up on ebay. Meanwhile, those of us who are not uptight about a little noise will be still using and autofocusing are "noisy" screwdrive lenses.