The Olympus OM-n models (single digit) have always been made for the professional market, the Pentax K1000 has always been made for the entry level amateur. Assuming two bodies of the same age, the professional body is superior purchase to the entry level body, all else being equal. The shutters and other components of pro bodies are designed to last for more total exposures. The frame of the camera of a pro body is manufactured to be sturdier, too.