Legacy vs E-Mount Lens IQ

I would look at things like bokeh, sunstars dictated by aperture blade count, also extreme circumstances.

My Leica 28mm Elmarit has no flare visible, even while pointing into glaring light. When I do that to a 1855 or even the Canon 2470, supposedly a very good zoom, I get huge purple fringes and flare all over the frame. Any lens can look reasonably respectful on a sunny day, but very few can hold up to a super-long exposure or shots with lots of contrast.

--
too lazy for DSLRs:-)