>>> do you think a mirror really makes you safer?

IMHO, a gotta' have. My most numerous close calls have been while wandering left into traffic. Anything you can do to spot that quiet vehicle is a good thing. [Happened just this morning in fact. Quiet car. . .spotted it.]

>>> what kind do you prefer?

Another vote here for Take-a-Look.

>>> clip-on is dorky looking though.

Agree, helmets too. . .tights too, but think about it. . . we're grown people riding bikes! Darn few cyclists can maintain a serious level of gravitas.