Ported vacuum comes from a small opening / passage that is slightly above the primary throttle blades at normal idle opening IE: 750 or so RPM with no radical camshafts that require more throttle opening at idle speeds.

As the throttle blades begin opening during acceleration the air passing by the opening begins drawing air (vacuum if sealed of hooked up to a non leaking vacuum advance. This is known as the venturi effect. See pic below. the red indicates air flow, the blue vacuum. As the throttle blades are opened, more air passes by the port and the vacuum increases adding more advance.
So there is no vacuum available at idle speeds .


Manifold vacuum ion the other hand is highest when the throttle blades are closed ( depending on camshaft) as the pistons are trying to draw air/ fuel against a restricted opening (the throttle blades). However it drops rapidly on acceleration due to the throttle blades opening. As one reaches cruising speed and the blade opening in relaxed the vacuum then returns to a higher state.
Which is better? I'm not going to open that debate.
To my knowledge Chrysler used ported vacuum in most applications. That may have changed during the emission years. hope this helps