One can easily become the other though it tends to act one way only. The major exception of nations being Greece.
Not a lot in it if you consider Germany 1933. After a democratic election, Hitler was appointed Chancellor and proceeded to 'democratucally' introduce 'The Enabling Act' of March 1933 which effectively transformed te democracy into a dictatorship.
You are perhaps confusing the act of transformation from one state to the other with the huge disparity between the two states.
Think of light and dark... easy to transform a windowless room from one to the other but the two conditions have no similarities.