Their biggest advantage by far is they are in. They play USC, UCLA home and home every other year. They can legitimately go after recruits that are PAC12 talent but might not want to compete with 5 star guys at USC and they can get them because they are in the club.
This also offsets the one true advantage BYU has over Utah and other P5s. The built in church connection for kids who want the religious experience. BYU gets their share of highly rated kids because those kids are LDS and want the BYU experience. KWhitt used to do a decent job of talking kids into the "you can get that at Utah anyway" approach but now that we are not on a level playing field and they are in the P5, the built in LDS advantage is highly neutralized.
This is why going back to MWC or another G5 conference is not the solution. That option doesn't address any of that.