Robert Bringhurst¹ prefers the en dash in the context of setting off phrases:
"The em dash is the nineteenth-century standard, still prescribed in many editorial style books, but the em dash is too long for use with the best text faces. Like the oversized space between sentences, it belongs to the padded and corseted aesthetic of Victorian typography.
"Used as a phrase marker – thus – the en dash is set with a normal word space either side."
¹https://archive.org/details/isbn_9780881791327/page/80/mode/...
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