Hate to jump on the necropost, but:
Originally posted by reh321 How does focusing under Live View differ from focusing while looking thru the viewfinder??
Originally posted by Na Horuk Viewfinder is Phase detect AF, which is the classical type. It uses AF module and has some points to select from. Points are tuned to some aperture rating
Live view cameras generally use Contrast detect, which uses CPU and simply maximizes edge contrast. It can do this for any area in frame. It is slower, but never suffers from back or front focusing, misalignment, etc. But it can still focus on the "wrong" object or it can simply not find enough contrast and will just hunt for focus. Some mirrorless cameras now have sensors with phase detect af points built-in, so that even live view would have some PD AF (but this technology is not very good so far; not as good as the highly evolved classical PD AF of DSLRs)
Additionally, depending on the camera and/or lens, the Live View focusing may actually be done with the lens at the selected aperture (rather than wide open through the OVF), which would eliminate issues with focus shift on lenses prone to it. Unfortunately, my K-30 doesn't do this (with native K-mount lenses); in Live View, it always seems to put the lens at some intermediate aperture around f/4 regardless of what is selected.
Don't know about other Pentax DSLRs.
Of course, this doesn't apply to adapted lenses with apertures that can't be controlled by the camera.