PEF is Pentax’s native RAW format, while DNG is Adobe’s more standardized RAW format. In practice, image data and editability are essentially the same, so there usually isn’t a quality advantage to either one.

The main differences are practical:

• Compatibility: DNG may feel more universal, but RAW software still needs camera-specific support either way. Most software that supports Pentax DNG also supports PEF.
• File size: On older Pentax bodies, PEF could be smaller because it used lossless compression while DNG was often uncompressed. On newer models, both are typically compressed, so the gap is much smaller.
• Workflow: If you use Adobe software and prefer working in DNG, shooting DNG can save a conversion step. If your current software handles PEF well, there’s little reason to switch.

So for a K-r, choose based on workflow and storage needs rather than image quality. Use DNG if you want a more standardized Adobe-friendly file. Use PEF if you prefer Pentax’s native format or find it fits your storage/workflow better.