The article and video didn't mention the best feature of it imo, being able to hold down on the keyboard to use it as a trackpad and move the cursor. Very useful for correcting typos easily, normally I'd delete the entire word as it was next to impossible to get the cursor after a letter in the middle of a word and now it's simple. Can see that being very time saving when writing long posts.
Besides 3D touch there's the A9 processor built on the 14nm scale which boosts performance and battery life (check out the Geekbench scores), 2GB RAM, better cameras in the back and front, 4K video shooting and much faster Touch ID (feels almost instantaneous compared to my 5s). All of that makes it a fools choice to go for the 6/6 plus rather than the S models.
Considering the aforementioned upgrades no "justifying" is necessary.
If they want to buy new it's okay. I am not against Iphones. But I would recommend to find a good deal with the Iphone 6/ 6 Plus
Besides 3D touch there's the A9 processor built on the 14nm scale which boosts performance and battery life (check out the Geekbench scores), 2GB RAM, better cameras in the back and front, 4K video shooting and much faster Touch ID (feels almost instantaneous compared to my 5s). All of that makes it a fools choice to go for the 6/6 plus rather than the S models.
Or do you just have to justify your new "big" "upgrade"?
Considering the aforementioned upgrades no "justifying" is necessary.