Almost every novice player starts out playing guitar using open chords. This makes chords fairly easy to play from a practical point of view but many players experience confusion around understanding chord construction later on.
The problem with open chords
Beginners learn open chords by name/shape association.
"This is a D", the books tell us. "and this is an A". Very quickly the association is made in the mind of the learner: this finger combination equals this chord.
However, open chords are dramatically inconsistent.
Some require 2 fingers, some require 3 and others 4 fingers on the fretboard. Worse still, there is no logic – all chords fretted with 2 fingers for example are not even the same chord type. And there is no visual pattern – chords with same fingering but starting on different strings are not the same e.g E and Am.
This makes it hard to see the commonalities in the chords. Present a few major chords, for example G D and C, and most beginners – because of the name/shape association – would be hard pushed to see any common properties defining them as major chords.
Sprinkle on the confusion caused by the tendency of beginners to accept chords as stand alone entities i.e. seeing E and Em as 2 separate beings, rather than variants of the same chord and the transition to a wider understanding of chords becomes all the more difficult.
Introducing chord types should come before open chords
If beginners were told of the relevant chord types that they would be using (for example major, minor and dominant 7th) and had it explained that all the open chords they were about to learn belonged in one of these categories, then it would lay the ground work for a better conceptual understanding of chord types. And novice players would understand that, just like a species, that chords may be categorised by their quality.
G, C, D, A, E are from the Major category
Em, Am and Dm are from the Minor category
G7, E7, A7, D7 are from the Dominant category
But where does that get us?
Put simply, a way for the beginner to organise their chords in a usable taxonomy. Instead of a blur of 12-15 seemingly unrelated chords, a basic compartmentalisation now groups them into easily digestable sets.
Why we should learn barre chords first
We won't, of course but if such a thing were possible, it would provide greater clarity.
Comparing a R6 major barre chord to an R6 minor barre chord, the beginner would clearly see the difference in chord types is only the distance of 1 fret for 1 of the notes. And one would hope the pattern would also be noticed for R5 chords.
Piano is more useful than guitar to teach chord construction
It just is. From a visual point of view all the notes are right there, and unlike a barre chords and most open chords the intervals are in numerical order which makes piano chord construction easier to grasp, plus piano chords make logical sense as they are played with 3 fingers - logically aligning with the 3 ingredients of basic major and minor triads.