opponents in conference play are at home.

If you look at Sagarin's ratings, SMU is the 7th best opponent we play (behind Utah, Kansas St., Oklahoma St., UCF, Kansas, and Arizona).
However, when you account for where each game is played, the game moves up (in Sagarin) to the 4th toughest game on the schedule (behind Utah, UCF, and Kansas St.).

Looking at FPI shows a similar situation (SMU being the 7th best opponent behind those same 6 teams, but being the 3rd toughet game behind Utah and UCF). Essentially, Kansas, Kansas St., Oklahoma St., and Arizona are all better teams than SMU, but since we get those 4 games at home they may end up being "easier" games due to the home field advantage.