Definitely not prestigious, but in most years those Pac10 teams are much stronger and more competitive than the Mountain West teams. I don't think anyone expects Air Force, UNLV, New Mexico, Wyoming, etc. to be as good as Cal, Stanford, ASU, Oreg. State, and so on. From top to bottom the Pac10 is stronger, especially if they add Texas, OU, and a handful of Big12 teams.
Pac10 has bigger schools, more money, more TV time, more exposure, all that jazz. If Boise really wanted to be taken seriously, they would step it up and join a real conference.