The best explanation for the relative significance of the trans-Saharan and Indian Ocean trade routes is: The routes were equally significant each in its own way as they both contributed to significant cultural developments along the routes, and worth cannot be measured simply by the goods that were traded.
Both trade routes facilitated not only the exchange of valuable goods but also cultural, technological, and religious exchanges that shaped the societies involved. Each route had its unique contributions and impacts that cannot be solely measured by the commodities traded.