the elmar 2.8 and summicron are both excellent choices for a start -- older summicrons may even have more problems than a newer elmar, ya never know.

You hear a lot about this or that lens being better or worse, but really, none are what you'd call bad unless they've got mechanical issues or have hazed up, which some can do My Elmar 2.8 was near mint but had some haze that actually turned out to be etching on an interior element by oil outgassing, needed a new element installed, was not cheap.

the Nokton is a Voigtlander/Cosina lens -- those take very nice pictures too and, being much newer, have a lot of computer optical engineering in them that older leica lenses didn't. I've got a 35 1.7 and a 16 4.5 and both are really lovely.

Get the lens that meets your needs best, not the one with the best reputation. The quality of the end product is 5 percent the equipment and 95 percent you.