Each friend (and three of the girlfriends) provide special unlockable abilities in return for maintaining good relationships with them.There are five friends in total, which become available at different times during the storyline.
Dating is much like hanging out with friends in that each girl has their own preferable activities.
Conversely though, Niko's choice of wardrobe and vehicular transport will also affect whether or not his date has a good time.
Both Michelle and Kate like Niko for who he is, so wearing something upscale (i.e., anything not from the Russian clothes store) and showing up in a flashy ride is typically to be avoided when dealing with either of them.
Nico can set up dates with three different women through the internet in addition to the two that he meets in the course of the storyline.
Once Nico has set up the date through their is a wait period and then he will recieve an e-mail from the date.