BYU went Independent for exposure. That was the #1 claim back in 2010. To dump the terrible MWC TV contracts. AAC has an ESPN deal through 2032, so the exposure aspect is still there.
Also, NY6 and playoff aren't the same, so comparing the past system access to a playoff isn't the same. NY6 bowl had a dead end. Playoff does not. And that improved access has real value. Because BYU would have a legit shot at the playoffs in the AAC, and very remote going for the 6 at-large as an Indy. Case in point--the 2020 teams doesn't get in. Best record since 1996 still doesn't get in.
$$$ will be about the same either way with Indy or AAC. BYU probably joins football only, so can negotiate the $$ the same with ESPN. THis would be a wash.
Control is the only point being in favor of staying Indy. If BYU value control above all else, you stay Indy. If they value the combination of exposure and playoff access they join the AAC, unless a P5 invite happens. Which is unlikely.
New landscape, new analysis. Under the new system, you have to consider the AAC now. You want that playoff access. Get that before Utah, more than Utah, and the script flips really fast locally, regardless of conference affiliation.