Not being a competition pilot myself I am not in the know regarding
this subject. But.......are there any soaring competitions held in the
U.S. where flying in the mountains is common for the whole course?

I've been told that pilots prefer the "safety" of desert or basin
flying since there are "more" places to land and that the separation
between ground and aircraft is greater.

One undisputed fact is that the scenery is better in the mountains.

Regards,
Brad