I'm not sure what we are trying to establish. If we are advising a potential musician the original advice that you can get away with very basic guitar playing whilst basic piano is pretty unsatisfactory as far as the listener is concerned. Nobody has pointed out that on a guitar you learn chords which is a start towards understanding scales and harmony. A friend and I who are both guitarists were trying to bring a pianist into the line up and they were lost without 'the dots'. Guitarists can shout chords at each other but this fairly well trained pianist had no idea what an 'F chord' was. They could play any sheet music in front of them but were lost without it.

And don't forget, no one ever took a piano to a campfire or beach. So if we are advising potential musicians go for guitar and then piano later if you like. And by the way I always advise acoustic guitar. An electric guitarist needs a band and you can't plug in at a beach or campfire!