I think the only argument pro-MWC people have, and it's true, is that the MWC schools mostly are in a regional footprint in which there are more BYU fans so more of them can go to the games. This probably explains the bigger fan turnout at the BYU away games compared to the WCC.
But I'm glad to give that up to get away from the trashy fans in the MWC that loathe BYU way worse than WCC fans.