One of the 5 G5 conference champions will make it every single year. And recent history (5 of the past 6 years) heavily favors the AAC champ.

If BYU were to join the AAC they would have to win their 6-8 team division, win a title game, and they are guaranteed to be one of 5 eligible teams for the final spot. And based off the current media love, they would have a strong leg up as the AAC champ to be chosen as the playoff participant. At worst, BYU could be playing on championship Saturday needing to win and have a game or two go their way.

As an independent BYU would likely have to go undefeated (something they have done once in nearly 100 years of football) or finish with 1 loss (something they have done four times) and then hope that BYU gets selected over a 2-3 loss SEC or Big 10 team. You can look at 3 loss Iowa State or Florida from last year to see how that would turn out for the Cougars.

I'm sorry but I don't see how those two paths are remotely comparable.