* Field of Study: BS degrees are overwhelmingly more common in STEM fields (Science, Technology, Engineering, Mathematics), while BA degrees are more prevalent in the humanities and social sciences. Therefore, comparing popularity requires specifying the field. If you're looking at all degrees together, the sheer number of STEM graduates might make BS degrees appear more popular, but that's a misleading comparison.
* Country: Different countries have different educational systems and cultural priorities, affecting the relative prevalence of BA and BS degrees.
* Level of Education: The comparison might change depending on whether you're looking at undergraduate, graduate, or postgraduate degrees.
In short, it's not a question with a simple answer. You need to specify the context (field of study, country, etc.) to make a meaningful comparison.