The consensus on 3 vs 1.75 is that 1.75 require less pressure to extrude.
This means there is an advantage with weak or direct drive extruders.
IME it also requires less pressure from the rollers in the extruder which means you're less likely to get stripping or slipping.
The reason everyone still uses 3mm is until recently it was a LOT cheaper and in some countries it still is, I was recently told that in the UK 1.75mm is 3x the cost per pound vs 3mm.
There is also a lack of well regarded hot-ends designed for 1.75.