I am debating the same question (which 28mm) and am glad that some much good advice is on this thread.
My comment may not answer the question but maybe help on making a decision. following the previous post.
I have used the VC 28mm f1.9 for over a year on an R-D1 and an M8, probably taking over 1,500 pictures.
The ones that came out of the cameras were very pleasing. They were sharp overall, in the centre even more, with no significant distortion and somehow drew beautifully when fully open. I usually take pictures of people and of landscapes: people (not portraits) were always successfully photographed with this lens.
My main issue with this 28mm was its size, which for me defeated the purpose of having a rangefinder.
I just sold it and I bought the CV 28mm f3.5 but haven't had a chance to test it.
From what I read, the Biogon, in which I am most interested, is rasor sharp in a "clinical" way and this doesn't suit everyone's taste, so this lens seems to be one that you want to have in addition to another one, providing more of a feel.
I hope to soom be able to own this lens to provide a better feedback.
All the best,
Alex