When I first got my 70-200mm HSM II, I wasn't impressed with the image sharpness on my K-5. However after I sent in my K-5 to Pentax Japan for focus adjustment, they replaced my K-5 with a new sensor unit. The nett result is this lens is now a lot sharper and focus is spot on, with no in-camera AF adjustments needed. The only other issue with this and some other Sigma lenses is the lens will not lock focus in live view and would require the lens to be re-chipped at a Sigma service centre. As to which version to choose, go with the cheapest. The lenses are sharp enough but make sure camera focus alignment is spot on. Many complaints of poor image sharpness could be due to the camera, not the lens.
Taken at the finish line at a local triathlon. K-5 + Sigma 70-200mm f/2.8 HSM II