Regarding BSI sensors compared to the previous design, I found the below, where the difference in pixel well opening appears quite big which suggests the superiority of the BSI technology regarding steep angles of light.
LCT @ DPReview posted links to the two images below, both shot with the Leica 21mm f/3.4 Super-Angulon lens @ f/5.6 and on Leica M 240 versus a thin sensor glass modded Sony a7RII.
