What is the difference between using a 1.75 mm filament or 3 mm sized filament
In simple word there is no big difference between 1.75mm and 3mm filament.
You're 3D printer's filament size should be matched with your nozzle size. larger the nozzle thicker the filament is good. Smaller the nozzle stick with thinner filament is good idea.
The only thing you really want to avoid is using 3mm with a small nozzle (0.35mm) you can get clog fast
Most of the jamming issues using 3mm filament with something like a 0.35mm Nozzle.
3mm works fine with 0.5 Nozzle, and a large nozzle will allow you to make larger prints faster. 1.75mm filament also can work fine with 0.5 nozzle, but assuming that it would be hard to feed filament quick enough.
But if you want to use a small nozzle like a 0.35mm. The pressure required to push 3mm through the smaller nozzle is something like to the power of 3 or 4, and it causes a lot of jamming. You want to avoid this. you realy need very good extruder module if you want to use 3mm filament with less then 0.4mm nozzle.
When people went down to a smaller nozzle, they started using 1.75mm filament to reduce the pressure required by the extruder (by reducing the cross-sectional area of the filament)
so its all happen with little research and experience. and now you will see more stick with 1.75mm filament. So pick your filament based on your nozzle size.
Pick your nozzle size based on how fast you want to print vs how high of a resolution you want. Accordingly you pick your filament size.
So The only thing to look out for though is the diameter of your nozzle. Smaller nozzles will have a harder time dealing with larger filaments and the other way around. It's best to see what type of filament your local suppliers offer