I like MBTI best, but even is only, at best, a suggestive template, not a personality dictate. It should be used to help understand one's cognitive preferences, not to define one's self or limit a person to a set of acceptable behaviors and thought patterns associated with that particular "type."
I think the best way and most credible way to understand human personalities is to interact with them in the real world and only use typology systems as a tool to help in that understanding. It's like typology systems are mere paint brushes. The art lies within the artist, not the brushes.