People usually describe HEXACO as "the Big Five plus honesty". That is half right and misleading in a way that matters. Honesty-Humility is genuinely new, but the two models also disagree about where to put anger and where to put sentimentality — which means they can describe the same person differently even on the factors that share a name. If you have taken both and the results look inconsistent, this is almost always why.
The Three Factors That Line Up
Extraversion, Conscientiousness and Openness to Experience mean roughly the same thing in both models. If you score high on Big Five Conscientiousness, you will very likely score high on the HEXACO version; the facet lists differ in detail but the territory is shared. For these three, comparing across models is reasonable and the research from one broadly informs the other.
This is worth stating plainly because it sets the scope of the disagreement. HEXACO is not a rival paradigm that rejects the Big Five — it is a refinement built with the same method on a wider language base, and most of it agrees. The interesting part is the minority that does not.
Where Anger Lives
In the Big Five, irritability and temper belong to Neuroticism, alongside anxiety and emotional instability. In HEXACO they do not: anger sits at the low end of Agreeableness, whose Patience and Gentleness facets are precisely about not being quick to hostility. HEXACO Emotionality keeps fearfulness, anxiety, dependence and sentimentality, and leaves anger out.
Take someone with a short fuse who is otherwise calm and untroubled — not anxious, not a worrier, but easily provoked. The Big Five will push them up on Neuroticism. HEXACO will push them down on Agreeableness and leave Emotionality unremarkable. Neither is wrong; they are different carvings of the same behaviour, and a reader who does not know that will think one of the tests malfunctioned.
Where Sentimentality Lives
The rotation runs both ways. Big Five Agreeableness includes a large warm, empathic, tender-minded component. In HEXACO much of that has moved into Emotionality, under the Sentimentality facet, leaving HEXACO Agreeableness as a narrower construct about tolerance and forbearance toward people who have provoked you.
So a deeply empathic person who nonetheless holds grudges may score high on Big Five Agreeableness and unremarkably on the HEXACO version, with their warmth appearing under Emotionality instead. This is why converting scores between models is unreliable, and why the honest answer to "what is my HEXACO Agreeableness given my Big Five profile" is that you should just answer the questions.
The Factor With No Counterpart
Honesty-Humility has no Big Five equivalent to compare against. Its content is scattered in a five-factor solution rather than absent, but scattered content does not produce a score, and this is exactly why HEXACO outperforms the Big Five in studies of unethical behaviour, exploitation and entitlement — it has a number for the thing being predicted, and the Big Five does not.
That is the practical rule for choosing. If your question involves fairness, integrity, greed or modesty, HEXACO has an answer the Big Five structurally cannot give. If it does not, the Big Five's larger literature is a real advantage. Details of the factor are in honesty-humility explained.
Which One to Take
For self-understanding, the honest answer is that the choice matters less than people expect: both give you six or five broad dimensions and a vocabulary for describing yourself, and both are descriptive rather than diagnostic. The difference shows up at the edges — in the two rotated factors and the one new one — not in whether the model "works".
If you have the patience, take both and read them side by side; the places they disagree tell you something the agreement does not. Start with the HEXACO test or the Big Five test, and use how to read your HEXACO results to avoid the standard interpretation traps.