My parents are in New Zealand on a lapto pc so it's Skype to them. My wife's got an iPhone and iPad so it's FaceTime mostly, but still use Skype no and then when on trips for work.
I use both all the time but I have to give the nod to Skype at the moment simply because I can engage multiple contacts over video and well as messaging or pulling content from another app. FaceTime is without a doubt easier to use but second strike is that the use is limited to wifi so once again Skype takes the win here. Another function is conference calling on Skype which at the moment does not exist on FaceTime.
I use skype just cause of video conferences for work,and haven't done much with the facetime app cause most friends aren't around an wi-fi all the time or they're very skeptical about JB to use facetime over their network.