When inserting a clause, which do you use? Em dash, parentheses, or commas? Are they in this situation as interchangable as they seem?

An example of the top of my head:

"When I entered the room—and I cannot believe I'm about to say this—I saw an orange goat."

OR

"When I entered the room (and I cannot believe I'm about to say this) I saw an orange goat."

OR

"When I entered the room, and I cannot believe I'm about to say this, I saw an orange goat."

I like the em dash the most. Parentheses in prose always struck me as odd, since I associate them more with numbers and academic writing than prose, and commas are already used in many other situations. And since I'm already asking, if you use the em dash as above, would it be better to be consistent and substitute semicolons with it, or to keep using semicolons precisiely to keep it different?

For example:

"Bed, desk, wardrobe; I saw nothing more."

OR

"Bed, desk, wardrobe—I saw nothing more."