Free vs. commercial

Free or commercial? That is the question. Since the beginning of my first font (which I still haven't finished), I have not been able to define my opinion of free vs. commercial licensing.

Therefore I have created this post; I'd really like to boil down the main arguments for selling a font/giving it for free. Does it depend from where you want to license it? Is it better to sell only the "Regular" font and give the rest of the family for free? What is the best option, if there's any?

Surely there are some posts linked with this discussion, but I couldn't find many...