I have a different opinion. I use a bucket hat because it has a smaller brim than a baseball cap (and, thus, better visibility) but still enough brim to shade my eyes so I'm not squinting all flight (especially on a blue day and even with good sunglasses).

If I am in a thermal with other gliders, I push the brim up (think Gilligan) so I have an unlimited upward view.

YMMV -

Lou