If you want a reliable vacuum signal, then take it from the manifold. This means the vacuum signal is averaged out and not subject to individual variations.
Manifold vacuum also means you’ll be less retarded at idle, so will be running more efficiently and generating less heat.
The only difference between ported vacuum and manifold vacuum is that the ported vacuum is manifold vacuum but with a missing or much depleted signal depending on throttle position. This also means it cuts in and cuts out more aggressively as throttle is opened or snapped shut. This is why I think people seem to think it is preferable to manifold vacuum.
Below is a link to graph of how much ported vacuum signal you get at various rpm as compared against ordinary manifold vacuum, from which it derives. The air pressure recorded at the ported vacuum port is mostly closer to atmospheric pressure in the airbox so there is less vacuum signal than the manifold vacuum would be, but the table doesn’t doesn’t tell you anything about the rate at which it cuts in or out.
Also appended is a graph of throttle opening versus vacuum (i.e. engine load). You’d expect the very top right hand corner to be 100%WOT. At 1700rpm, under full load, the throttle is 51% open, i.e. the engine is effectively at WOT if only half open at 1700rpm because the engine is getting all of the air it needs at that throttle opening.
These should give you a feel for how much vacuum signal you can expect under what circumstances of throttle opening. Numbers are absolute- 100kPa = 1atmosphere at sea level, so 60kPa = 40% vacuum.
kind regards
Marek