so many pros and con arguments!
here are practical examples with the NEX6 and the Zeiss Makro-Planar 120mm/4, studio flashes
this is the "monster"
click for larger image
this is a studio example:
(you can find it here flickr - mouse over for details on the flickr image)
two 1:1 crops
click for the real 1:1 crop
and one more with this 120mm Makro-Planar
and the 1:1 crop