In your case, I'd say stick with APS-c. For one thing, the K-P is pretty close to the K-1 in noise, because of the accelerator chip. Most of the time I can't tell the difference between APS-c images and my FF images unless I look at the exif.
The biggest disadvantage I see for you is your lack of FF lenses.
I actually started collecting FF lenses long before the K-1 was available, so I had a good stable fo FF lenses when I bought the K-1.
Lenses I've bought specifically for the K-1 (because all those older lenses came with their own set of issues)
DFA 28-105, DFA 100 macro, DA*55 1.4, and Tamron AF ED 300 2.8.
That's a lot more money than what you're paying for your camera. And I really didn't like the camera all that much before I bought the DFA 28-105 which in my mind is the cheapest zoom that let's you explore all the K-1s capabilities, the way I shoot.
On the other hand, for birds, wildlife, macro, etc. I'm still using a K-3 for most images. Image wise, the K-P is better than what I'm using and I still find it advantageous. Part of my logic for getting the K-1 was Pixels shift and the flippy back screens and GPS. Two of those things are covered by the K-P and if you want GPS, you can add it on.
I have prints up to 30x20 taken with the K-1 and K-3. They are all good. No loss of quality unless you go really really big, and no one seems to know how big you have to go to make a difference.
So if it were me, I'd go with the K-P.
But I have no doubt either will make you happy.
Last edited by normhead; 06-15-2019 at 06:10 PM.