I've always preferred the look of low flange, myself. But that's just me. Although, they do look nice if they are polished mirror bright!

But what others have said is right: High flange hubs reduced the length of the spokes, resulting in a stiffer wheel. They were mainly used for track bikes and tt-specific bikes, etc.

Craven: The hubs themselves weighed a tad more (if my old-fart memory is working correctly today), but the (less) weight of the shorter spokes offset it.