Both conferences have similar (and small) media shares from the conferences, about $500,000 per team. https://www.on3.com/news/conference-tv-deals-current-status-college-football/
Historically the Sun Belt has been the lowest status BCS level teams.
We are heading into a time though when almost all the conference contracts will be coming up at once. Based on the markets they are in the Sun Belt looks to be better placed than C-USA. Also with some teams building success the Sun Belt looks to have more national appeal
Louisiana finished the season ranked, Coastal Carolina was ranked much of the season, Appalachian State has been ranked has been one of the better G5 programs.
C-USA has multiple programs that are sinking or have sunk.
Prospects for future contracts are in favor of the Sun Belt
Simply put Sun Belt has the ESPN family of channels including ESPN+. C-USA has CBS Sports Network and it doesn't take a rocket scientist to know that the SBC has the better media rights deal even if the per school payout is the same.
It's also very obvious how both conferences treat football. It just makes no sense to treat football as a second class citizen when it is the sport that makes up a significant chunk of the valuation of media rights deals.