i think the whole discussion is entirely aesthetic and personal. The combination of sensor type, pixel density, processing algorithms, the noise reduction technology available at the time and the awb biases of each camera in my opinion all combine to give a particular "look". Example: Some people prefer some "grain" or "noise", some dont. Then of those that do, some "types" of noise will appeal and some wont.
There is no question in my mind that the k10 produces a different vibe in some shots than later camera's. My father bought a k20. We both think my k10 makes more appealing images. Neither of us can say why, its just there. My k5 produces a different vibe again, sometimes for better and sometimes not. It sounds arbitrary -probably because it is, lol- but the "mood" of the two camera's are different for whatever reason. Interestingly, the k3 invokes more k10 vibe for me when i view the shots, even though the nature of how ccd noise and cmos noise is handled within an image differs. Purely to my eye. Purely personal. Where some are claiming "worse" noise on the k3 than the k5, i think it adds lovely ambience to shots and is closer to the filmish grain of ccd. So really, i should probably get off my backside and buy one, lol.
Just on ccd's in general, Leica still use one in certain models. It may not be coincidence that they chose the 18mp ccd for the Monochrom rather than the 20 or 24 mp cmos. There might be a hint there that tonal differences do indeed exist in the rendering abilities of the two.
But its all so subjective and really, who cares? We all love Pentax. Use whichever model(s) makes us happy. I love all three of mine for different reasons. And will likely add a fourth.
Last edited by saladin; 01-24-2015 at 08:16 PM.