I had both lenses for quite some time.
The pre-asph Lux was a Titanium one. It was very soft at 1.4 and glowed a lot, however at f2 it was very sharp, comparable to by FLE. From 2.8 onwards it had, however, a small focus-shift and at 2.8 and 4 it was slightly less sharp than at f2. My copy was perfectly calibrated. Contrast was much higher than the 8 elements, but colours were rendered very accurately.
The 8 elements is softer than the pre-asph Lux at f2, with some glow, but very usable wide-open. I feel that for portraits it gives them a nice vintage feeling, but significantly sharper than the pre-asph Lux wide open. From 2.8 onwards it is much sharper than the pre-asph Lux and shows absolutely no focus-shift. Colours have a lower saturation maybe due to the fact that contrast is quite low. The fact that this lens can show up shadow detail that others can't is very much true and is a consequence of the combination of high-resolution and low-contrast, a feature it shares with the Type 2 Rigid Summicron from the same era. I feel that these low-contrast/high-resolution lenses shine particularly on digital sensors and B&W film. For colour film, higher contrast lenses give nicer results.
The fact that the Summicron could be focused at 70 cm and could use a screw-on filter (I use my lenses without a hood) sealed the deal for me.