70mm: This is probably the most disturbing part of test for L owners... The difference between L and IS is huge, L can't reach the sharpness of wide open IS at any aperture. IS wins hands down here...
100mm: The difference is not as huge as at 70mm, but L still can't reach sharpness of IS, which is clearly better even wide open (f4.5) than L stopped down at f8.
135mm: IS wins again, although very tight.
200mm: L is better here. Stopping down helps a lot, while IS is constantly soft, no matter what aperture you set.