There’s another problem: Not all the personality traits delineated by the Five Factor theory are positive. One of the traits in this framework is neuroticism, for example, which has undeniably negative associations.
One of the major selling points of Myers-Briggs is that it is unequivocally positive. No personality type in its framework is better or worse than any other; each is billed as having unique and constructive strengths.
I'll go further than this. Most of what I know about the Big Five comes from Geoffrey Miller, and in his telling, only openness, agreeableness, contientiousness, stability, and extraversion are unequivocally good. Their opposites are all bad.
As an introverted, not-especially-open individual, I bristle at this characterization. But that aside, I will remind readers of the singular virtue of intelligence tests over personality tests: they cannot be gamed (much). If, say, employers started using high-stakes Big Five questionaires, job seekers easily discern how to use their answers to indicate "good" traits over "not good" traits. Myers-Briggs, in happy contrast, provides little incentive to do this.