Much different recruiting base. The PAC 12 had California Arizona Utah Oregon and Washington and now Texas as their hotspots. Lots of inner city and large numbers to pick from. More speed and athleticism in skill positions. The Big12 has a Texas-Midwest recruiting. More physical and hard working easy to coach recruits. Similar to what Utah has done in the past.
Last year Colorado (pac12) was the only team that our defense struggled with. Our defense matches better with Big12 offenses. Where we struggled was on offense. Our small frail WR were unable to get through the contact allowed on the outside. More physical play on the d- line and linebackers nullified our power run game. Hopefully the spread offense and a quarterback that can run and extend plays where the receivers can get separation will help. Losing a bigger receiver like Williams really hurts. I expect more motion and roll out pass run options which is what the pac12 did to give us problems defensively.