My father has been bugging me to take some side by side pictures between the 2 cameras to see the difference. I finally got off my butt and did a unscientific study.
I started with the K7, set both cameras to manual and RAW. Both shots took with my Magnicon 70-210. I picked something in the middle of the zoom range of the lens, and used same F stop, zoom, focusing distance, shutter speed, tripod, timed shutter release etc, to try to get both cameras to take the same shot. My framing on both shots was off somewhat, but I was rushing to make sure lighting didn't change. I imported pictures out of camera into LR. Both imported with same treatments and WB set to Daylight, then crop of both pictures. K7 is first.
K7
*istD
K7 crop
*istD crop