One factor Nikon has brought with the D5 and the D500 is the implementation of UHS-II for SDXC and the use of XQD format which is basically the replacement for Compact Flash cards. I had forgotten about the XQD format. When I did a google search a
PentaxForum Poll thread was one of the hits from the summer of 2012. It did not garner much attention back then.
XQD is/was clearly the way to go in hindsight. Reading up about it it does spec out much better than SD in the long run and the short. So it is interesting that Nikon has already included XQD in the dual slot D500. The Nikon D4 has already been using it. The specs for the Nikon D500 has the overall physical dimensions at 147x115x81 just around about the size of the Pentax FF. The D500 is ~1.5cm taller and wider than the K3ii.
The D500 will not out perform the K3ii on image quality. Sharpness alone the K3ii will be hard to beat using pixel shift even in the limited capacity it can be used. The D500 should excel at video over the K3ii. Due entirely over the K3ii only having a UHS-I interface.