I scarcely glance at the camera screen after taking a shot, if at all. When using flash I might check it to confirm that the flash did fire, and that I got the flash formula right if I am in manual. I certainly would not trust using the camera display to decide which are the keepers between similar shots. On a big screen I often see small details, hardly distinguishable on the camera display, which might be the deciders - for example where the camera focus was optimum in a busy street scene, whether on one particular person or another.
I just upload the lot to my PC, it is a single movement. I can then view them how I like, depends on your software, and I can make my decisions in a calm and unhurried environment. I don't understand why deciding on the rejects on the PC should take any longer than it does on the camera, in total.
Having said all that, I'm surprised that Pentax cannot provide the side-by-side facility for the benefit of people who want it. It is only a bit of software, and I'm not going to die in a ditch trying to denying it to anyone who does want it (thinking back to the flippy screen flame wars
).