It's much smaller than the K series cameras like the K1000, yet with professional features such as interchangeable focusing screens. It can partner well with the slightly larger and more feature-laden LX. It's the same size as the ME and its kin, but more attuned to the needs of the serious photographer.... I am unfamiliar with the MX camera model, other than that it uses the bayonet mount Pentax lens. What are the other prime reasons you find, to own this camera model?