Full review will be coming in the next few weeks. These compares right now are quick analysis I use and compare the two lenses. Please see Compare #1 posted earlier.
For round #2, I have 4 SOOC shots for you today. Zeiss on the left, Leica on the right. Top row is wide open, second row is f/5.6. These were all taken at ISO 160 through Leica M-E on a tripod. See below for individual images. Take note of the subtle yet present vignetting of the two top images (Zeiss 1.5 / Leica 1.4). I'd suggest opening the crops below in separate tabs and switching between them - the differences begin to stand out.
Carl Zeiss C Sonnar 1.5/50 @ 1.5
Leica Summilux-M 1.4/50 ASPH @ 1.4
Carl Zeiss C Sonnar 1.5/50 @ 5.6
Leica Summilux-M 1.4/50 ASPH @ 5.6