depends what you want to do. would you want to go into academia, get an engineering job, do consulting/finance/government policy, etc? If you know for sure you just want to get into an engineering job, purdue might be a good fit. Columbia will give you much more options in what you would like to do with your career in the future (yes, as bad (or not) as it is, the ivy title does help, especially in really snotty places like consulting/finance/think tank locations). and why do you think 22 is a low ranking (i do not think it is?)? That being said, the overall living, research, lab, and culture fit should be driving your decision, not rankings.