Whether we like it, or acknowledge it, or not, there is no fair comparison. Even a 'pristine' original steel rim Summilux is at least 56 years old. Coatings oxidise, and even optical glass flows. There is no brand new, straight from manufacture comparison. Even if you have negatives that you shot with a brand new steel rim back in the day, we can no longer get those films. So we can't compare old and new. When the differences in characteristics of the old lens get emphasized vs the characteristics of the new lens in reviews, remember that you cannot compare like with like. Lead containing flint glass is not magic, in fact it is just optical glass with lead in it that was the best material available at the time (but is not any longer). While I agree that old lenses produce beautiful images (I love my rigid 50mm Summicron) I can't help but think that all the effort put into comparisons would be better put into taking pictures.
I plan to sell my original steel rim and get the new one, just to have a newer lens.
Marty