It really makes little sense in the age of conference realignment to pretend conferences don't control the strength of their conference schedule just as much as non conf. Some have more power than others but conferences control the in conference schedules on a whim just as much as teams control their non conference.
Big 12: We have the best conference and toughest schedules because Big Ten and SEC passed on elite top ten basketball programs like Arizona, Kansas, Baylor and Houston while we added several elite basketball programs. We actively made our conference schedules better and created the first/only POWER ONE conference.
Big East: They added UConn, they added Creighton, they've been trying to make their basketball conference tougher for decades, if it's Power 2 Big East is the 2.
SEC: They've chosen to be a so so average basketball conference. They could have added Arizona, KU, Baylor and Houston within or near their geographic footprint and immediately they are #1 or close to Big 12 for #1. They didn't. They chose so so A&M, Texas, and OU. Next time they expand they'll again ignore basketball for football.
Big Ten: They could've added KU, ISU, UConn, Arizona, etc... instead they chose to add Nebraska, USC, Washington, Penn State over the years. UCLA is a sleeping giant but they suck the past few decades compared to the programs they've clearly passed on.
Gonzaga: They could have joined the MWC decades ago and actually played a good conference schedule. Instead they choose a joke conference schedule.
ACC: They consistently passed on #1 basketball program of the past quarter century UCONN. They added 3 crappy basketball programs recently...they made their schedules even worse next year. Further back they consistently passed on good program WVU when WVU needed a home.