Pipe bands have all kinds of different uniforms and uniform headgear. In some, pipers wear Glens and drummers wear Balmorals. In others, that's reversed. In some, they all wear the same style headgear, but some wear diced and some plain. In the band I play with, we all wear plain Glens.

The Royal Regiment of Scotland wears diced Glengarries when in parade dress (as do the pipe bands when they're not in their "no. 1's" - with feather bonnets or bearskins).

Dicing supposedly means loyalty to the House of Hanover.

Wear what you like the looks of, as long as you understand some people may question your "right" to wear it. (That goes for a lot of other things in Highland clothing as well.)