This is a popular myth.
B1G and Big 12 are basically the same, as evidenced by the .500 head to head record over the years.
Over the years? The B1G today is not the same as the one last year (has improved), and the B12 of today is also not the same as last year (regressed by a lot). The B12 is a collection of mid to low tier teams from the form B12 and Pac12 conferences. The line play is nowhere near equal, nor the physicality. A big 12 team could beat a B1G or SEC team in a one game scenario (preseason or postseason).. but to string multiple games together in a season... no chance. With no headliners in the conference, I'd imagine this year will be their best year... While they will continue to sink further into irrelevancy as time goes on. It'll become proving grounds, a stepping stone for players and coaches to step up to the B1G and SEC.
Also, of course I do not like Iowa, nor should anyone, and we should always be hopeful that the cyclones beat Iowa. However, the one reason why the Iowa Sate game seems to always be close is because firstly it is rivalry game and secondly its early in the season when Iowa is at their worst.