Redwing, your post reminds me of a funny lens story that may or may not help you...
A few months ago I was hired to shoot a graduation for a local college. Cool, i thought, so I rented a couple of L series Canon lenses -- the good stuff. The stuff the mega-pros use.
After the graduation, I did a curious test. I shot a series of shots with the expensive L series lenses and an identical series of shots with a $75 kit lens. I showed those shots to 14 people (five of whom take pictures for a living). Not one person could tell a significant difference (at least with the naked eye). Actually more people picked the "kit lens" pictures as the better pictures.
What does all this mean? Who knows. But after this little experience and talking to a number of my pro photo buddies, I don't sweat lenses no where near as much as I used to.
One photographer I know, a 30 year veteran and former war photojournalist remarked: "Asside from build quality and much wider apertures, there ain't much difference in the glass." And I've read more than a few articles that seem to suppor this.
Take it for what it's worth...
Good luck with your decision.
I am not trying to say you are wrong here, just giving my opinion.
There are differences in the glass, in some cases very large ones.
I own 4 EF-S lenses, 1 normal EF lens, and 3 L lenses.
Most (if not all) L lenses use UD, super UD, and or Flourite elements. They have special optical properties, and they reduce chromatic aberration, which improves image quality.
L lenses are made to tighter tolerances, and they use the best materials and craftsmanship for the glass and housing.
L lenses almost always have better sharpness than non L lenses with a few exceptions. The 60 macro for example is extreemly sharp, although its a non L lens.
I own the EF 28-200 3.5-5.6 and it is a total piece of junk. Soft as a marshmallow, especially in the corners. I wish I had never bought it.
When I first tested my L lenses, I was blown away by the improvements in image quality over my EF-S lenses. This was especially true for the 70-200mm 2.8L IS II, which is optically outstanding in just about every way.
I understand what you are saying about not noticing the differences.
This is probably because the images weren't enlarged to anything close to their actual pixels.
If you zoom down to actual pixels, you will notice the rather significant differences. This is especially true when comparing the best L lenses vs. the worst EF (or EF-S) lenses.
If you are interested in all the details of this stuff, buy the official Canon EF Lens Work III book.
It is cheap and very useful for helping you to understand why exactly L lenses are so good, and what it takes to make them. :mrgreen: