These are extremely sloppy (I left the Nikon at 6400 the whole time, and skipped 3200 with the Pentax) quickie tests of some of the theorized roundabouts between the two formats.
a. DOF, especially close up work.
In this application 6400 is not so good -- I would not choose to use it, but was too lazy to put a faster speed on it. F4 on the Pentax gets the lens in focus while f/5.6 doesn't on the Nikon.
b. Nikon AF is more consistent than Pentax, and quicker. Nikon did hunt less, and to my eye, with the 6400 noise, seems to have hit the dancer's face consistently. Pentax hunted a bit and there was one total miss (as usual attributable to a sloppy camera operator). Lenses are the DA 16-45 f/4 and 24-120 3.5-5.6 AF-D Nikkor; both older but quality lenses. Pentax has SR on, the Nikon lens is not VR.
c. At 6400 FF beats APS-C. Unfortunately I screwed up and didn't shoot a 3200 series; so I can only present a 1600 vs 6400 test.
d. DOF -- the FF at 5.6 has about a stop shallower DOF -- see below, I did manage to stop the Pentax down to f4.
These are 100% crops all
Same set, this time the full image. Overall point of view etc. Pentax metered much darker and warmer than Nikon (given the standard settings) and I had to do a ~ +1.3/1.4 adjustment with the center slider on levels.
So yeah, this proves beyond a doubt that most of the time it is the photographer's inattention and incompetence that is the deciding factor in image quality and proper usage of each format. It also points out some 'house flavor' in the two manufacturers' view of how to automate. And finally, originally I'd thought of pitting the DA 70 against the Ai 105/2.5 manual focus lens, but I simply got too lazy.