I haven't been able to put both the Avenon 28mm 3.5 MC and the CV 28mm 3.5 through similar paces, but wanted to report back on some thoughts on initial impressions having had a look at results from both.
The Avenon 28mm 3.5 MC
Size/handling: Possibly one of the smallest lenses available in LTM mount, rivalled only by the MS optical triplet. This does not, however, mean that it's a fiddly lens. The focus tab is well positioned, and the aperture ring is always out of the way, until you need to use it. Recessed optics are a big plus for using the lens without a filter, and the wide OEM hood does little in the way of adding bulk, but does limit access to aperture ring when on as I have wider hands/fingers. Depth of field scale is easily read. Seems to be a brass/alloy hybrid build. Smooth focusing and aperture mechanisms, though not built to leica-tight tolerances (though this may be due to age and normal wear and tear).
Performance: I did not shoot on full frame digital with either lens, so no idea how they performs there. On film the Avenon has an aesthetic I like very much, and the flare performance is amongst the best. As sharp as it needs to be at all apertures with minimal softness at far corners. Supposedly a hand made lens, so, impressive to say the least. 1m minimal focus distance is was limiting on very few occasions.
The Voiglander Color-Skopar 28mm 3.5
Size/handling: Like the Avenon, it's a tiny lens, but this one has a "cone" build, wide at base, narrowing towards front. It sits taller than the Avenon. Nice focus tab, but narrow and not as comfortable to rest a fingertip on like the Avenon's tab. This lens is a bit more fiddly to use, but nothing that gets in the way, it just feels more cramped despite its larger size. Depth of field scale less clear. Solid brass construction, and like others have already said, one of CV's best technical build efforts. Smooth focusing and aperture controls and very well designed/compat screw in hood.
Performance: Again, on film, this lens seems to have struck a serious balance between modern performance, and medium contrast. It's as sharp as it needs to be, but on an X-Pro 1 on a tripod and compared to the Avenon, it showed slightly different rendering (micro contrast differences?). Flare performance also excellent. Negligible light falloff at edges. .7m minimum focus distance allows for a much closer shot. 30cm on a 28 is a significant difference.
Final thoughts
These are two very capable performers at a very similar price point. I would not hesitate with either one, though I do prefer the Avenon's handling. It will be hard deciding to let either one go.