Well sure but "all thing being equal" is what someone who is considering whether to go for further schooling is considering. I'm me, I have all my qualities, would I be more likely to be hired (and get a higher wage) w/ a BS or w/ a PhD? That's why I pose it that way and that's why I ask for what your answer to this problem is, it's not about who you would pick, it's about what drives people to "overachieve" in their credentialling in the first place.