which lens do you feel render better at mid-distance? Is it a different lens design that is the cause/benefit?
Strictly at 35mm?
I would say the Sonnar 35/2 (unfortunately glued on the RX1 body), 35/1.4 ZA, Sigma 35/1.2 and CV 35/1.7 have smooth transition zone (some more than others) which is needed for more pleasant rendering at mid-distance. This is not related to the amount of blur they are capable of achieving. Usually spherical aberration under-correction is the main contributor for this.
I just ordered the Sony 35 1.8 to see if it can replace my Batis 40. I need something that can do close focus distance and also has nice out of focus rendering for general shooting.
Well I have only had mine for a couple days but tested sharpness vs my 24gm and 50 1.4. At least my copy held it's own nicely. I'm not an extreme corners pixel peeper. If someone is looking at my pictures and there eye goes to the extreme corners then my composition sucked, it's not the lenses fault The sonnar is still my favorite but I have given up on that lens making out of the RX1. This lens is close enough for me. I'm glad I ignored some of the comments on FM and tried it out. Almost didn't. Just sold both the 24 and 50. I had the 24 covered with the tamron 17-28 anyway and plan on picking up the CV50 APO to replace the Zeiss. Rendering will be the compromise and little slower but the trade off is smaller/lighter and still sharp and I'm OK with that.