What degree is more prestigious BS or BPS?

There's no standard degree called "BPS." A "BS" (Bachelor of Science) is a common and widely recognized undergraduate degree. Therefore, a BS is far more likely to be understood and acknowledged than a non-standard abbreviation like BPS. If you encountered "BPS," it's likely a program-specific abbreviation for a particular institution or field, and its prestige would depend entirely on that institution and program's reputation.