IB challenged me, both in terms of difficulty and volume of work, which served as great preparation for both university and work afterwards. Perhaps even more valuable than the knowledge itself, are the habits of persistence, time management and hard work that one is forced to develop going through the IB program.
Some students choose to take regular classes compared to IB based on the hypothesis they can achieve higher grades; that might be true, but it misses the point. The habits of humility, persistence, and working together with peers that are required to succeed in university and beyond are the most valuable aspects of the IB program. Focusing on the best opportunity to obtain high grades is short-term thinking; IB is an investment that will pay off for many years to come.