It prob is best to play 4-3 for 1 season but practice both. Then in second season switch to 3-4 and stop practicing 4-3.
That being said, I have had excellent success switching to 3-4 and playing it in first season. Like another poster said , I believe quality of talent can overcome low form iq. Up to a point. I have made it to the NC but didn't win it.
One thing I am convinced of , It makes a Much Larger Difference switching to an Offensive formation and playing it in first season of practicing it than it does a Def one. Low form iq on offense and you throw lots of interceptions.