`—` or `—` is there any difference in HTML output?

Question

— or —

Is there a difference between these? Is one better-supported than the other?

Answer 1

From W3 web site Common HTML entities used for typography

For the sake of portability, Unicode entity references should be reserved for use in documents certain to be written in the UTF-8 or UTF-16 character sets. In all other cases, the alphanumeric references should be used.

Translation: If you are looking for widest support, go with —