that they would never again have a winning season on joining the Pac12 but that BYU would be left behind, they'd probably get about a 90% vote in favor of moving. I believe the best thing for most Utah fans about being in the Pac12 is that BYU got left behind. Had BYU gone with them or signed on to the Big12, there wouldn't be nearly the amount of Pac12 stickers or discussion about conference afitation. Other than discussing which conference is better.
I should add that if the roles were reversed that BYU fans would also hold conference affiliation over the Utah fan base, though not to the degree that Utah has to us.