Electronically, should single or several ground pins be used?
There are times when you want a single ground point (star grounding), separate grounds with filters (separate analog and digital grounds, for instance), or you just don't care (99% of the time).

Regardless, this is usually a concern when you are laying out a circuit on a PCB. When you already have a PCB the grounds become a moot point because the PCB dictates how they operate.

For a module like an Arduino, unless otherwise stated, all grounds are equal and can be used for whatever whenever.