I hate to break your notion about posture, but I believe the second picture has overall better posture than the first one. The first picture has the neck brought back, which tips the ribcage and brings the lower ribs out, causing the lower spine to curve, as opposed to the second picture where the lower spine should be straighter. This goes along with the idea that all fascia should be stretched to their proper length and taut, whereas if the lower spine curves, the fascia of the lower back goes limp and I believe the same happens for the neck if you bring it back. Look up "Delsarte, Alexander, Masoero, You" on YouTube. He has great videos about posture and how the fascia work in regards to it (though I haven't verified myself whether the fascia are more taut in the posture he advocates for). The second picture mimics the posture he talks about, though the chin is a bit lifted, and the back of the neck could be lifted instead.