I did the same between my 16" and the 2016 15.4" of my parents. everything maxed out, they were incredibly similar. The 2016 one had no True Tone, I tried to calibrate the screen by eye to match with the warmth of the 16". The 15.4" one had a tiny bit more contrast but at the expense of less detail (I compared using the background pic 'Catalina-Silhouette' and on the 16" one I could make out slightly more details on the rocks than on the 15.4").
I really like the True Tone feature on the 16" because on the 2016 15.4" I needed to set a couple of calibrated profiles as color temperature changes throughout the day.
What surprised me was that the 16" screen looked noticeably bigger! Also my tech-averse parents noticed that.
I upgraded my machine from a 2012 15.4" retina MBP with 8GB RAM. A great machine that served be incredibly well in different jobs. The 16" one feels like a smooth evolution. The new keyboard has the same underlaying technology but feels even nicer. Of course it is a lot more responsive. Battery life is incredible. I love the Touch Pad. The reduced amount of ports doesn't bother me because even with the 2012 I needed to have adapters for VGA, so I simply have a multi-port adapter now and that's it. I like the Touch Bar as well but it's more of a gadget than a tool.
Config: I took an i9 with 2.4 GHz, 32GB RAM, 2TB HD and the 5500m/8GB graphics.
All in all - the 16" is a warmly recommended machine!