Is an ellipsis interchangeable with an em dash?

I know than an ellipsis can be used to show a broken sentence, the same way an em dash can be used. What I don't know is that if the two are interchangeable and it is writer preference or if different meaning is conveyed by their use.

Are ellipses and em dashes commutable?

To my mind, there is a clear difference in pronunciation between the two: the em-dash is a clipped break, or a very abrupt shift, while the ellipsis is a distinct pause with a bit of elongation of the prior syllable.

If you take a sample sentence of

Wait... there may be something.

vs.

Wait—there may be something.

then for the first one, the word "wait" has a downward intonation, and a slightly drawn-out "ayy" sound; and there is a clear pause, possibly a full inhalation, before starting to say "there". It tends to have more of a connotation of thoughtfulness.

For the second one, "wait" is more emphasized, with no downward intonation, and is somewhat clipped; there is still a short pause before starting to say "there" but there is definitely no inhalation. It tends to have more of a connotation of urgency.

While I can certainly see your logic, I would say for that use (i.e. at the end of a broken sentence) ellipses are used for intentional pauses after a full, complete, unbroken sentence and dashes are used for unintentional breaks before a sentence is finished.

I would never-

vs.

I would never do that...

A hyphen is just an indication that someone was cut off before they were done talking.

To me, an ellipses is a pregnant pause. It says "There is some significance in what I said, so I'm following it with a pause for emphasis."

This makes me wonder why people put ellipses after every line in texts.

According to Wikipedia, the em dash "demarcates a break of thought."

An ellipse is more commonly used to imply either a possible continuation or an unfinished thought.

I guess that, in certain cases, the two may be interchangeable.