http://ascii.jp/elem/000/000/632/632158/
(in Japanese)
The full size original ISO head-to-head comparison is at the page two:-
http://ascii.jp/elem/000/000/632/632158/index-2.html
(Excite machine-translated to English)
So, here we go. Of course, the GXR wins. But how big is the difference? Okay, it's your take now and I let you decide! :-)
Last but not least, other real-world samples are posted, different settings and functions are tested. All of the samples are full-sized ones and they are directly out of the two cameras.