Sailor Ted,
Do a search in the Leica M forum and you will several discussions relative to this.
I had a 35 Cron ASPH that I sold after purchasing the Lux ASPH. IMHO they are two completely different lenses.
I live in AZ which has very contrasty light, that just does not work well with the Cron. The Cron was too contrasty, and blocked up the shadow detail. I also did not like its OOF rendering as well, since it did not transition slowly at all but rather a sharp cut-off.
The Lux is less contrasty, but just as sharp. It provides a little more shadow detail and I much prefer its transition from focused to OOF areas. You also have the extra stop which is very useable.
I think that you will find the contrast and rendering of the Lux much more pleasing on the digital sensor.
Check out some of the posts by Magus on this subject as he is much more eloquent than I am. We had this discussion before here on this forum and the LUF also. Just before selling the Cron, I did a direct set of comparison photos for him between the two lenses.
Do some searching of photos and pick which ever suits your taste the best.
The Cron & Lux are NOT the same lens with only a stop difference. They render completely differently.
Best,
Ray