Nex6 versus Nex5N

I can answer to that

Its the jpeg NR pattern that is different. on low ISO's 5n is just tad better, but on high ones (12800) 5n is worse. 5n has that big smudge colorpaint look to them. So in the end its tradeoff.

Nex 6 ISO 6400: (focus seems bit off here)

5n ISO 6400:

Nex 6 ISO 12800:

5n ISO 12800