Al Kaplan - Miami, FL , Feb 22, 2003; 05:57 p.m.
Think of them as tools for doing a job. Some lensmounts are sturdier than others, some lenses are sharper than others, some have better bokeh or better contrast, some may sacrifice maximum sharpness at smaller apertures in favor of performance wide open. To some extent "pro" grade lenses are designed to hold up better to hard use than "consumer" grade optics. Some independant brands have actually marketed lenses from several manufacturers under one brand, and the same lens with slightly different knurling on the control rings may appear under more than one label. There are no absolutes.
When I was a college student (that was about 12 years after they first invented colleges) we used to try to buy good quality used equipment. There's a lot of pro grade Canon, Nikon, and similar stuff going begging today for a fraction of what it should be worth because it won't couple with the latest whizz-bang auto exposure systems or isn't auto focus. It's a buyers' market if you want fairly new top quality equipment, and can think for yourself and turn a ring or two before pushing he button. The truth is, it's harder to defeat the automation in some cameras for creative purposes than it would be to just set a manual camera yourself. Leicaflex and Leica R (reflex)cameras and lenses are the bargain of the century on the used market.