Originally posted by Ash Pentax's incremental upgrades are slight but deliberate and calculated. The FF model might well come out to be 24 Mp and thus have minimal benefit over the K-5 on paper, but practically, there may be more to it than meets the eye - high ISO capability, good size/weight for a FF camera, and a slick AF system.
A 24MP FF will have ~40-50% better resolving power on the same lens as the K-5.
The FF will have more control over DOF (unless you're shooting at F/22 on APS-C).
The noise will be better if you tolerate or want smaller DOF.
The viewfinder will almost certainly be bigger and brighter.
Tracking moving subjects will be easier while maintaining equal resolution.
The AF point will be smaller for the same AF-point-performance, meaning that AF will be more precise inherently.