3 points
I was curious, so I looked it up.
iPhone 6 Plus frontal area: 158.1mm x 77.8mm = 12,300mm²
iPhone 15 frontal area: 147.6mm x 71.6mm = 10,568mm²
iPhone 15 Plus frontal area: 160.9mm x 77.8mm = 12,518mm²
So (TL;DR:) the 6 Plus is 16% larger than the current iPhone, and 1.75% smaller than the current Plus model.
In the past decade, phones haven’t actually got bigger, despite people online saying they have. Screens have, while the bezels have shrunk.