A few usually has a positive connotation, and few usually has a negative connotation.

Let’s say I’m moving to a new city, and I say “I have a few friends there.” – that’s a good thing; I know some people so I will have a good time in the new city.

Now let’s say my son is not very popular in school. I would say, “He has few friends.” – that’s a bad thing; he has only 2-3 friends, and it would be better for him to have more friends.