There are microcontrollers (for example all the ATmega chips as far as I know) that allow ports to be set to "output", "input tristate" or "input internal pull-up resistor".
What are the advantages/disadvantages of either of those options in case of not connected pins? As I know, leaving them on output is the worst solution. The chips are shipped (I think) with all ports as input, tristate.
I'm asking specifically about the situation where those pins are not soldered anywhere. (or possibly soldered to ground, but the general case should be not soldered anywhere)