I would take the Pentax in f/2.8 for the extra half stop of aperture. Full compatibility with every mode that the camera has is a bonus too.
Are Leitaxed lenses a manual aperture deal? If so, bear in mind that manual apertures are an acquired taste. I use my K mount lenses on my Samsung NX bodies. No big hardship but one must make allowances. At least on mirrorless the body cranks up viewfinder brightness when you stop down. On a DSLR you have to focus wide open, stop down, take meter reading, you know the drill. Just like granddad with his Spotmatic and Takumar lens, but he managed just fine.