Mark,
The Tessar is a great lens which can be pretty sharp while not being too harsh (in some forms).. either the pre-war Tessars for being fairly sharp but still dreamy, or the post-war (eg Contaflex) examples which produce a lovely sharp but less saturated look than modern lenses. I only don't use Tessars more because they're a bit slow for snapshots of stuff like low-light music or dancing. The other quick-ish 6 and 7 element lenses would be quick enough and affordable but I don't really know much about them..
Btw, while not the lens people want, the late examples of the Triotar in Contax mount are pretty decent if not priced for collectors.. and even if a once-in-a-lifetime deal on a late 85mm Sonnar comes along, the Triotar is nicer to carry and use most times when F4 is enough.
To the Mods, I figured this would be a bit more general than the Contax forum, though my Sonnar is in Contax mount - was hoping for more of a general Sonnar vs other great (but not quite top dream) European 40's to 60's production lenses..
I can find some discussion and comparisons to the Summicron, Summilux, and original Nokton, but not much on the models just a bit more affordable and common, or produced between the most revolutionary models.
This could be because they weren't direct competitors at the time - or for slr and rangefinder etc, but nowadays with available adapters and all falling into the category of vintage lenses, it seems interesting to compare a few more of them which can nowadays theoretically be mounted to the same body.
I have seen some talk linking the Xenon to the Summitar, and that the Ultron is an improved Xenon with a high level of sharpness. I've also seen comments recommending a Sonnar over a Summitar for a holiday, but I don't really have any idea how an Ultron compares to a vintage Sonnar, or whether a Xenon would work nicely for the sharp but slightly dreamy, slightly lower contrast pictures I tend to like.
On some level part of me would also like a (vintage) sharper but not perfect 50mm F2 for available-light action shots - different options for some specific circumstances.