While I know everyone's different, it seems to me that the archetype characters imply internal consistency.
In a story when someone represents this aspect faithfully it represents how individuals solve problems better than complex characters. What I mean is when I'm deciding on how to solve a problem, let's say with my kids, my heart says one thing and my mind says another. I have to weigh those against each other. Sure, my heart may be influenced by my reasoning, and logic will always be restrained by that-which-is-kind.
But if the archetype represents the GENERAL approach it represents life better. For example Guardian. A guardian, which in Dramatica carries morality, is the heart+mind+truth character. (Conscience, evaluation, equity). But a complex emotion character might even confuse people. We look for patterns in life. It makes us feel balanced. It gives us confidence when we make a decision.
The reader, in looking at a grand story argument, can sense the tension between mind and heart, or between the guardian and mind, or between antagonist's avoid/reconsider and the same thing the guardian does in his own way.
It seems to me that the archetypes used right, and flavoring the characteristics rather than completely changing them, makes for a stronger argument and more consistency with life.
I found this after I wrote this reply, which confirms my spinning thoughts about archetype character: