You can make Michigan as rigorous as you wish…as rigorous as Northwestern if that is your desire. Ross with a double major in Mathematics for instance. Michigan’s Mathematics program, factoring in its Honors Sequences, is considered one of the top 5 in the nation. As such, you can get the academic/intellectual rigor that you desire and in the end, benefit from the professional placement of Ross. You could even double major in Economics and Mathematics and minor from Ross is you prefer. As such, I do not think a degree from Northwestern is more “versatile”. You cannot go wrong with either really. NU and Michigan can both give you the intellectual and academic challenge that you seek and, in the end, the professional placement that you desire. Go with your gut.