Instead of trying to identify each chord's unique sound as a whole, we can break it down and identify it by its intervals.
This method of chord detection is more objective and preferred. However, it requires the ability to break harmonically played chords down to interval by ear. It also requires a familiarity with chord patterns.
Let's illustrate this by comparing between Major & minor chords:
To distinct between the chords, we should focus our listening on the 3rd degree. While in Major chord the 3rd degree is a Major 3rd interval, in Minor chord it's a minor 3rd: