No tests here.....and I am no scientific shooter...but I have owned the K5 -K5IIs...and now the K1.
I'll give you my thoughts from my experience with all three ...which is extensive .
The K5IIs was a huge improvement over my K5....both in IQ and in shooting abilities...mostly the AF was better and the high ISO shooting was greatly improved. I was very satisfied with this camera until it fell off the shelf and was badly damaged. At that point I opted to go for the K1.
I shoot mainly wildlife nowadays and almost exclusively in the K1 Crop Mode....so to me it is very close to what I got out of the K5IIs. Maybe a little better color, better high ISO results by a stop...sometimes two.......but the main advantage is the greatly improved AF...and the much better SR.
Old story I have told many times here, but maybe you haven't heard it, so here goes....
I have shot for over 10 years using a 50-500 Bigma...the old model and now the newer HSM OS model. With either one the Bigma has hunted with AF like a blind hound. The lower the light the worse the hunting.It has driven me insane(er) so many times I could not possibly count the shots Ihave missed while the Bigma hunts back and forth to lock focus. You know, wildlife won't hang around for you to get a decent focus, so you are limited to those times you can get lucky.
Here comes the K1...I unbox it, have a battery ready to go and the Bigma ready to mount. As usual, there is always a bird or squirrel handy outside my office windows.......let's see what happens? I'll be damn! Focus was instant and it locked on the subject even though it was in heavy brush! This is amazing...must be a fluke or I just got lucky? Nope, it does it every time and has since that moment...good light or bad it finds the target and locks on it ...fast!
You have no idea what a difference this has made in my shooting pleasure......and I curse 80% less than I did before the K1! There are so many great features on the K1...and many I may never use but it's nice to know they are there anyhow. But.....if none were there except this magical AF it would be enough to make all the difference if I was buying a new Pentax.
The Bigma is a FF lens.....but I shoot in the Crop Mode with it. It is more like the K5 series in results and I love the way the Crop Mode functions. Simply turn the dial and set to Crop and you're there! You get a nice heavy black outline of the crop frame and when you half press focus is instant and you know exactly what you see is what you get....saves so much time in cropping while processing and gives better results in my experience.
At that half press the
frame beeps and goes bright red...you know you have locked focus and can snap your shot.....all almost instantly. Few shots are missed with the K1.
The SR is magical too....you can really drop the speed even with the big slow Bigma and still retain sharpness. It is a lifesaver at times of low light!
Having said all of that, the end result is about the same as with my K5IIs.....a little better, but that depends on the circumstances of the shot more than the sensors I do believe? Of course,with the K1 you will get a ton more decent shots, and with the greatest of ease....that makes a huge difference to me!
Here is a gallery at Flickr with shots from the K5-K5IIs...and K1. They all have EXIF so you can see which is which....take a look and it may answer your basic question. I don't think you should expect amazingly better results with the K1 if you shoot as I do, but you will most definitely get your shots with greater ease and enjoy the shooting to a much greater extent!
I post the good, bad, and ugly here...so no one shot is indicative of the particular camera used.
https://www.flickr.com/photos/129469263@N03/albums/72157651162955781
Hope this was of some help to you!
Regards!
Rupert