Originally posted by biz-engineer K1 ii, better in low light, without hesitation.
This.^ I judge I am getting 1-1/2 to 2 stops of lower noise or higher ISO with my K-1 II over my still excellent KP.
Then there is the matter of build quality and reliability, not subject to the aperture block problem, as well as features and more advanced controls, battery life even without a battery grip, also there is enhanced image quality with the same framing- really no comparison in all of these factors. The K-1 II is a thoroughly professional model in every respect. Of course you'd need lenses that fit your needs. If you primarily shoot from some distance and are using lenses in the tele range, APS-C would be advantageous. In that case, go for a KP if not the new K-3 III. Otherwise, there are very fine FF lenses available, even many used manual focus lenses of high quality. I'm sure you've thought about lens needs in considering the K-1 II at all. Since you are not as likely to have a special need for lighter carrying for this kind use, the weight difference of FF should not pose much inconvenience. If I were doing that job, unless I needed a lot of tele I'd take my K-1 II.